diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index ae512f085cc8..df38d94bc0bd 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -52,7 +52,7 @@ repos:
                 frmts/pcidsk/sdk|
                 frmts/grib/degrib/degrib|
                 frmts/grib/degrib/g2clib|
-                ogr/utf8.h|
+                port/utf8.h|
                 ogr/ogrsf_frmts/cad/libopencad/|
                 ogr/ogrsf_frmts/geojson/libjson/|
                 ogr/ogrsf_frmts/flatgeobuf/flatbuffers/|
diff --git a/apps/gdaltindex_lib.cpp b/apps/gdaltindex_lib.cpp
index 68c15081642c..8bec93493ed2 100644
--- a/apps/gdaltindex_lib.cpp
+++ b/apps/gdaltindex_lib.cpp
@@ -147,7 +147,7 @@ static bool PatternMatch(const char *input, const char *pattern)
         }
         else
         {
-            if (tolower(*pattern) != tolower(*input))
+            if (CPLTolower(*pattern) != CPLTolower(*input))
             {
                 return false;
             }
diff --git a/autotest/cpp/data/utf8accents.txt b/autotest/cpp/data/utf8accents.txt
new file mode 100644
index 000000000000..a0c35d225c7a
--- /dev/null
+++ b/autotest/cpp/data/utf8accents.txt
@@ -0,0 +1 @@
+ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÑÒÓÔÕÖÙÚÛÜÝßàáâãäåæçèéêëìíîïñòóôõöøùúûüýÿĀāĂ㥹ĆćĈĉĊċČčĎďĐđĒēĔĕĖėĘęĚěĜĝĞğĠġĢģĤĥĦħĨĩĪīĬĭĮįİıIJijĴĵĶķĸĹĺĻļĽľĿŀŁłŃńŅņŇňŌōŎŏŐőŒœŔŕŖŗŘřŚśŜŝŞşŠšŢvŤťŦŧŨũŪūŬŭŮůŰűŲųŴŵŶŷŸŹźŻżŽž
diff --git a/autotest/cpp/data/utf8accents_ascii.txt b/autotest/cpp/data/utf8accents_ascii.txt
new file mode 100644
index 000000000000..4444beb5ac42
--- /dev/null
+++ b/autotest/cpp/data/utf8accents_ascii.txt
@@ -0,0 +1 @@
+AAAAAAAECEEEEIIIINOOOOOUUUUYSSaaaaaaaeceeeeiiiinoooooouuuuyuAaAaAaCcCcCcCcDdDdEeEeEeEeEeGgGgGgGgHhHhIiIiIiIiIiIJijJjKkkLlLlLlLlLlNnNnNnOoOoOoOEoeRrRrRrSsSsSsSsTvTtTtUuUuUuUuUuUuWwYyYZzZzZz
diff --git a/autotest/cpp/test_cpl.cpp b/autotest/cpp/test_cpl.cpp
index 6dbeabda9806..c96777518efb 100644
--- a/autotest/cpp/test_cpl.cpp
+++ b/autotest/cpp/test_cpl.cpp
@@ -5129,4 +5129,79 @@ TEST_F(test_cpl, CPLStrtod)
     }
 }
 
+TEST_F(test_cpl, CPLForceToASCII)
+{
+    {
+        char *pszOut = CPLForceToASCII("foo", -1, '_');
+        EXPECT_STREQ(pszOut, "foo");
+        CPLFree(pszOut);
+    }
+    {
+        char *pszOut = CPLForceToASCII("foo", 1, '_');
+        EXPECT_STREQ(pszOut, "f");
+        CPLFree(pszOut);
+    }
+    {
+        char *pszOut = CPLForceToASCII("foo\xFF", -1, '_');
+        EXPECT_STREQ(pszOut, "foo_");
+        CPLFree(pszOut);
+    }
+}
+
+TEST_F(test_cpl, CPLUTF8ForceToASCII)
+{
+    {
+        char *pszOut = CPLUTF8ForceToASCII("foo", '_');
+        EXPECT_STREQ(pszOut, "foo");
+        CPLFree(pszOut);
+    }
+    {
+        // Truncated UTF-8 character
+        char *pszOut = CPLUTF8ForceToASCII("foo\xC0", '_');
+        EXPECT_STREQ(pszOut, "foo");
+        CPLFree(pszOut);
+    }
+    {
+        char *pszOut = CPLUTF8ForceToASCII("foo\xc2\x80", '_');
+        EXPECT_STREQ(pszOut, "foo_");
+        CPLFree(pszOut);
+    }
+    {
+        char *pszOut = CPLUTF8ForceToASCII("foo\xc2\x80x", '_');
+        EXPECT_STREQ(pszOut, "foo_x");
+        CPLFree(pszOut);
+    }
+    {
+        std::string s;
+        {
+            VSILFILE *f =
+                VSIFOpenL((data_ + SEP + "utf8accents.txt").c_str(), "rb");
+            ASSERT_NE(f, nullptr);
+            VSIFSeekL(f, 0, SEEK_END);
+            s.resize(static_cast<size_t>(VSIFTellL(f)));
+            VSIFSeekL(f, 0, SEEK_SET);
+            VSIFReadL(&s[0], 1, s.size(), f);
+            VSIFCloseL(f);
+            while (!s.empty() && s.back() == '\n')
+                s.pop_back();
+        }
+        std::string sRef;
+        {
+            VSILFILE *f = VSIFOpenL(
+                (data_ + SEP + "utf8accents_ascii.txt").c_str(), "rb");
+            ASSERT_NE(f, nullptr);
+            VSIFSeekL(f, 0, SEEK_END);
+            sRef.resize(static_cast<size_t>(VSIFTellL(f)));
+            VSIFSeekL(f, 0, SEEK_SET);
+            VSIFReadL(&sRef[0], 1, sRef.size(), f);
+            VSIFCloseL(f);
+            while (!sRef.empty() && sRef.back() == '\n')
+                sRef.pop_back();
+        }
+        char *pszOut = CPLUTF8ForceToASCII(s.c_str(), '_');
+        EXPECT_STREQ(pszOut, sRef.c_str());
+        CPLFree(pszOut);
+    }
+}
+
 }  // namespace
diff --git a/autotest/ogr/ogr_gpkg.py b/autotest/ogr/ogr_gpkg.py
index 394ca882730c..28ef09e51411 100755
--- a/autotest/ogr/ogr_gpkg.py
+++ b/autotest/ogr/ogr_gpkg.py
@@ -10489,3 +10489,23 @@ def test_ogr_gpkg_ST_Area_on_ellipsoid(tmp_vsimem):
         ) as sql_lyr:
             f = sql_lyr.GetNextFeature()
             assert f[0] is None
+
+
+###############################################################################
+# Test LAUNDER=YES layer creation option
+
+
+@gdaltest.enable_exceptions()
+def test_ogr_gpkg_launder(tmp_vsimem):
+
+    tmpfilename = tmp_vsimem / "test_ogr_gpkg_launder.gpkg"
+
+    ds = ogr.GetDriverByName("GPKG").CreateDataSource(tmpfilename)
+    lyr = ds.CreateLayer(
+        "az+AZ09_", options=["FID=MY_FID", "GEOMETRY_NAME=MY_GEOM", "LAUNDER=YES"]
+    )
+    assert lyr.GetName() == "az_az09_"
+    assert lyr.GetFIDColumn() == "my_fid"
+    assert lyr.GetGeometryColumn() == "my_geom"
+    lyr.CreateField(ogr.FieldDefn("_"))
+    assert lyr.GetLayerDefn().GetFieldDefn(0).GetNameRef() == "x_"
diff --git a/autotest/ogr/ogr_pg.py b/autotest/ogr/ogr_pg.py
index 0e904fd8b2f1..1845381d3b76 100755
--- a/autotest/ogr/ogr_pg.py
+++ b/autotest/ogr/ogr_pg.py
@@ -5911,3 +5911,45 @@ def test_ogr_pg_schema_case_createlayer(pg_ds, tmp_schema):
             pg_ds.CreateLayer(f"{tmp_schema_mixedcase}.yet_another_layer")
     finally:
         pg_ds.ExecuteSQL(f'DROP SCHEMA "{tmp_schema_uppercase}" CASCADE')
+
+
+###############################################################################
+# Test LAUNDER=YES
+
+
+@gdaltest.enable_exceptions()
+def test_ogr_pg_LAUNDER_YES(pg_ds, tmp_schema):
+
+    eacute = b"\xC3\xA9".decode("utf-8")
+    lyr = pg_ds.CreateLayer(f"{tmp_schema}.a" + eacute + "#", options=["LAUNDER=YES"])
+    assert lyr.GetName() == f"{tmp_schema}.a" + eacute + "_"
+    lyr.CreateField(ogr.FieldDefn("b" + eacute + "#"))
+    assert lyr.GetLayerDefn().GetFieldDefn(0).GetNameRef() == "b" + eacute + "_"
+
+
+###############################################################################
+# Test LAUNDER=NO
+
+
+@gdaltest.enable_exceptions()
+def test_ogr_pg_LAUNDER_NO(pg_ds, tmp_schema):
+
+    eacute = b"\xC3\xA9".decode("utf-8")
+    lyr = pg_ds.CreateLayer(f"{tmp_schema}.a" + eacute + "#", options=["LAUNDER=NO"])
+    assert lyr.GetName() == f"{tmp_schema}.a" + eacute + "#"
+    lyr.CreateField(ogr.FieldDefn("b" + eacute + "#"))
+    assert lyr.GetLayerDefn().GetFieldDefn(0).GetNameRef() == "b" + eacute + "#"
+
+
+###############################################################################
+# Test LAUNDER_ASCII
+
+
+@gdaltest.enable_exceptions()
+def test_ogr_pg_LAUNDER_ASCII(pg_ds, tmp_schema):
+
+    eacute = b"\xC3\xA9".decode("utf-8")
+    lyr = pg_ds.CreateLayer(f"{tmp_schema}.a" + eacute, options=["LAUNDER_ASCII=YES"])
+    assert lyr.GetName() == f"{tmp_schema}.ae"
+    lyr.CreateField(ogr.FieldDefn("b" + eacute))
+    assert lyr.GetLayerDefn().GetFieldDefn(0).GetNameRef() == "be"
diff --git a/autotest/ogr/ogr_pgdump.py b/autotest/ogr/ogr_pgdump.py
index ec92a8491889..fddb6cf7bfe5 100755
--- a/autotest/ogr/ogr_pgdump.py
+++ b/autotest/ogr/ogr_pgdump.py
@@ -1580,6 +1580,66 @@ def check_and_remove(needle):
     )
 
 
+###############################################################################
+# Test LAUNDER=YES
+
+
+def test_ogr_pgdump_LAUNDER_YES(tmp_vsimem):
+
+    eacute = b"\xC3\xA9".decode("utf-8")
+    filename = str(tmp_vsimem / "test_ogr_pgdump_LAUNDER_YES.sql")
+    ds = ogr.GetDriverByName("PGDump").CreateDataSource(filename)
+    lyr = ds.CreateLayer("a" + eacute + "#", options=["LAUNDER=YES"])
+    lyr.CreateField(ogr.FieldDefn("b" + eacute + "#"))
+    ds = None
+
+    f = gdal.VSIFOpenL(filename, "rb")
+    sql = gdal.VSIFReadL(1, 10000, f).decode("utf8")
+    gdal.VSIFCloseL(f)
+    assert '"a' + eacute + '_"' in sql
+    assert '"b' + eacute + '_"' in sql
+
+
+###############################################################################
+# Test LAUNDER=NO
+
+
+def test_ogr_pgdump_LAUNDER_NO(tmp_vsimem):
+
+    eacute = b"\xC3\xA9".decode("utf-8")
+    filename = str(tmp_vsimem / "test_ogr_pgdump_LAUNDER_NO.sql")
+    ds = ogr.GetDriverByName("PGDump").CreateDataSource(filename)
+    lyr = ds.CreateLayer("a" + eacute + "#", options=["LAUNDER=NO"])
+    lyr.CreateField(ogr.FieldDefn("b" + eacute + "#"))
+    ds = None
+
+    f = gdal.VSIFOpenL(filename, "rb")
+    sql = gdal.VSIFReadL(1, 10000, f).decode("utf8")
+    gdal.VSIFCloseL(f)
+    assert '"a' + eacute + '#"' in sql
+    assert '"b' + eacute + '#"' in sql
+
+
+###############################################################################
+# Test LAUNDER_ASCII
+
+
+def test_ogr_pgdump_LAUNDER_ASCII(tmp_vsimem):
+
+    eacute = b"\xC3\xA9".decode("utf-8")
+    filename = str(tmp_vsimem / "test_ogr_pgdump_LAUNDER_ASCII.sql")
+    ds = ogr.GetDriverByName("PGDump").CreateDataSource(filename)
+    lyr = ds.CreateLayer("a" + eacute, options=["LAUNDER_ASCII=YES"])
+    lyr.CreateField(ogr.FieldDefn("b" + eacute))
+    ds = None
+
+    f = gdal.VSIFOpenL(filename, "rb")
+    sql = gdal.VSIFReadL(1, 10000, f).decode("utf8")
+    gdal.VSIFCloseL(f)
+    assert '"ae"' in sql
+    assert '"be"' in sql
+
+
 ###############################################################################
 # Cleanup
 
diff --git a/doc/source/drivers/vector/gpkg.rst b/doc/source/drivers/vector/gpkg.rst
index cf33fb484284..319278304ad7 100644
--- a/doc/source/drivers/vector/gpkg.rst
+++ b/doc/source/drivers/vector/gpkg.rst
@@ -342,6 +342,21 @@ Layer creation options
 
 The following layer creation options are available:
 
+-  .. lco:: LAUNDER
+      :choices: YES, NO
+      :default: NO
+      :since: 3.9
+
+      Whether layer and field names will be laundered. Laundering makes sure
+      that the recommendation of https://www.geopackage.org/guidance/getting-started.html
+      is followed: an identifier should start with a lowercase character and
+      only use lowercase characters, numbers 0-9, and underscores (_). UTF-8
+      accented characters in the `Latin-1 Supplement <https://en.wikipedia.org/wiki/Latin-1_Supplement>`__
+      and `Latin Extented-A <https://en.wikipedia.org/wiki/Latin_Extended-A>`__
+      sets are replaced when possible with the closest ASCII letter.
+      Characters that do not match the recommendation are replaced with underscore.
+      Consequently this option is not appropriate for non-Latin languages.
+
 -  .. lco:: GEOMETRY_NAME
       :default: geom
 
diff --git a/doc/source/drivers/vector/pg.rst b/doc/source/drivers/vector/pg.rst
index 0a9e1c2749c0..2e5e26c5e7c8 100644
--- a/doc/source/drivers/vector/pg.rst
+++ b/doc/source/drivers/vector/pg.rst
@@ -268,6 +268,18 @@ Layer Creation Options
       some special characters like "-" and "#" to "_". If "NO" exact names
       are preserved. If enabled the table (layer) name will also be laundered.
 
+-  .. lco:: LAUNDER_ASCII
+      :choices: YES, NO
+      :default: NO
+      :since: 3.9
+
+      Implies LAUNDER=YES, with the extra substitution of UTF-8 accented
+      characters in the `Latin-1 Supplement <https://en.wikipedia.org/wiki/Latin-1_Supplement>`__
+      and `Latin Extented-A <https://en.wikipedia.org/wiki/Latin_Extended-A>`__
+      sets with the closest ASCII letter. Other non-ASCII characters are
+      replaced with underscore.
+      Consequently this option is not appropriate for non-Latin languages.
+
 -  .. lco:: PRECISION
       :choices: YES, NO
       :default: YES
diff --git a/doc/source/drivers/vector/pgdump.rst b/doc/source/drivers/vector/pgdump.rst
index 7fd0ad96be28..4a689aca4649 100644
--- a/doc/source/drivers/vector/pgdump.rst
+++ b/doc/source/drivers/vector/pgdump.rst
@@ -63,8 +63,19 @@ Layer Creation Options
       layer to have their field names "laundered" into a form more
       compatible with PostgreSQL. This converts to lower case and converts
       some special characters like "-" and "#" to "_". If "NO" exact names
-      are preserved. If enabled the table
-      (layer) name will also be laundered.
+      are preserved. If enabled the table (layer) name will also be laundered.
+
+-  .. lco:: LAUNDER_ASCII
+      :choices: YES, NO
+      :default: NO
+      :since: 3.9
+
+      Implies LAUNDER=YES, with the extra substitution of UTF-8 accented
+      characters in the `Latin-1 Supplement <https://en.wikipedia.org/wiki/Latin-1_Supplement>`__
+      and `Latin Extented-A <https://en.wikipedia.org/wiki/Latin_Extended-A>`__
+      sets with the closest ASCII letter. Other non-ASCII characters are
+      replaced with underscore.
+      Consequently this option is not appropriate for non-Latin languages.
 
 -  .. lco:: PRECISION
       :choices: YES, NO
diff --git a/frmts/netcdf/netcdfdataset.cpp b/frmts/netcdf/netcdfdataset.cpp
index b170b0e65823..68cf0c28cad4 100644
--- a/frmts/netcdf/netcdfdataset.cpp
+++ b/frmts/netcdf/netcdfdataset.cpp
@@ -3425,14 +3425,14 @@ void netCDFDataset::SetProjectionFromVar(
         for (unsigned int i = 0;
              i < strlen(poDS->papszDimName[poDS->nXDimID]) && i < 3; i++)
         {
-            szDimNameX[i] = (char)tolower(static_cast<unsigned char>(
+            szDimNameX[i] = (char)CPLTolower(static_cast<unsigned char>(
                 (poDS->papszDimName[poDS->nXDimID])[i]));
         }
         szDimNameX[3] = '\0';
         // for( unsigned int i = 0;
         //      (i < strlen(poDS->papszDimName[poDS->nYDimID])
         //                        && i < 3 ); i++ ) {
-        //    szDimNameY[i]=(char)tolower(static_cast<unsigned char>((poDS->papszDimName[poDS->nYDimID])[i]));
+        //    szDimNameY[i]=(char)CPLTolower(static_cast<unsigned char>((poDS->papszDimName[poDS->nYDimID])[i]));
         // }
         // szDimNameY[3] = '\0';
     }
diff --git a/frmts/pcidsk/sdk/core/pcidsk_utils.cpp b/frmts/pcidsk/sdk/core/pcidsk_utils.cpp
index 169c3891ff48..45c1dbd7f256 100644
--- a/frmts/pcidsk/sdk/core/pcidsk_utils.cpp
+++ b/frmts/pcidsk/sdk/core/pcidsk_utils.cpp
@@ -40,6 +40,12 @@
 #include <cstdarg>
 #include <iostream>
 
+extern "C"
+{
+int CPL_DLL CPLToupper(int c);
+int CPL_DLL CPLTolower(int c);
+}
+
 #if !defined(va_copy) && defined(__va_copy)
 #define va_copy __va_copy
 #endif
@@ -104,8 +110,7 @@ std::string &PCIDSK::UCaseStr( std::string &target )
 {
     for( unsigned int i = 0; i < target.size(); i++ )
     {
-        if( islower(static_cast<unsigned char>(target[i])) )
-            target[i] = (char) toupper(static_cast<unsigned char>(target[i]));
+        target[i] = (char) CPLToupper(static_cast<unsigned char>(target[i]));
     }
 
     return target;
@@ -409,10 +414,8 @@ int PCIDSK::pci_strcasecmp( const char *string1, const char *string2 )
         char c1 = string1[i];
         char c2 = string2[i];
 
-        if( islower(static_cast<unsigned char>(c1)) )
-            c1 = (char) toupper(static_cast<unsigned char>(c1));
-        if( islower(static_cast<unsigned char>(c2)) )
-            c2 = (char) toupper(static_cast<unsigned char>(c2));
+        c1 = (char) CPLToupper(static_cast<unsigned char>(c1));
+        c2 = (char) CPLToupper(static_cast<unsigned char>(c2));
 
         if( c1 < c2 )
             return -1;
@@ -447,10 +450,8 @@ int PCIDSK::pci_strncasecmp( const char *string1, const char *string2, size_t le
         char c1 = string1[i];
         char c2 = string2[i];
 
-        if( islower(static_cast<unsigned char>(c1)) )
-            c1 = (char) toupper(static_cast<unsigned char>(c1));
-        if( islower(static_cast<unsigned char>(c2)) )
-            c2 = (char) toupper(static_cast<unsigned char>(c2));
+        c1 = (char) CPLToupper(static_cast<unsigned char>(c1));
+        c2 = (char) CPLToupper(static_cast<unsigned char>(c2));
 
         if( c1 < c2 )
             return -1;
diff --git a/frmts/pds/pds4dataset.cpp b/frmts/pds/pds4dataset.cpp
index dd532d3676f4..9862a3ea01bb 100644
--- a/frmts/pds/pds4dataset.cpp
+++ b/frmts/pds/pds4dataset.cpp
@@ -1421,7 +1421,7 @@ static CPLString FixupTableFilename(const CPLString &osFilename)
     if (!osExt.empty())
     {
         CPLString osTry(osFilename);
-        if (islower(static_cast<unsigned char>(osExt[0])))
+        if (osExt[0] >= 'a' && osExt[0] <= 'z')
         {
             osTry = CPLResetExtension(osFilename, osExt.toupper());
         }
diff --git a/gcore/gdal_mdreader.cpp b/gcore/gdal_mdreader.cpp
index 2d78e4de842c..18684e492c9e 100644
--- a/gcore/gdal_mdreader.cpp
+++ b/gcore/gdal_mdreader.cpp
@@ -1031,7 +1031,7 @@ static bool GDAL_IMD_AA2R(char ***ppapszIMD)
             CPLString osLine;
             osTarget.Printf(
                 "IMAGE_1.%c%s",
-                tolower(static_cast<unsigned char>(keylist[iKey][0])),
+                CPLTolower(static_cast<unsigned char>(keylist[iKey][0])),
                 keylist[iKey] + 1);
 
             osLine = osTarget + "=" + osValue;
diff --git a/gcore/gdal_misc.cpp b/gcore/gdal_misc.cpp
index 0e9feaad5da8..a00be33fda88 100644
--- a/gcore/gdal_misc.cpp
+++ b/gcore/gdal_misc.cpp
@@ -2316,9 +2316,9 @@ int GDALReadWorldFile2(const char *pszBaseFilename, const char *pszExtension,
     for (int i = 0; szExtUpper[i] != '\0'; i++)
     {
         szExtUpper[i] = static_cast<char>(
-            toupper(static_cast<unsigned char>(szExtUpper[i])));
+            CPLToupper(static_cast<unsigned char>(szExtUpper[i])));
         szExtLower[i] = static_cast<char>(
-            tolower(static_cast<unsigned char>(szExtLower[i])));
+            CPLTolower(static_cast<unsigned char>(szExtLower[i])));
     }
 
     const char *pszTFW = CPLResetExtension(pszBaseFilename, szExtLower);
diff --git a/ogr/ogr_srs_pci.cpp b/ogr/ogr_srs_pci.cpp
index 089720c2dd00..67f650a61a81 100644
--- a/ogr/ogr_srs_pci.cpp
+++ b/ogr/ogr_srs_pci.cpp
@@ -236,7 +236,7 @@ OGRErr OGRSpatialReference::importFromPCI(const char *pszProj,
 
             if (nCode >= -99 && nCode <= 999)
                 snprintf(szEarthModel, sizeof(szEarthModel), "%c%03d",
-                         toupper(static_cast<unsigned char>(*pszEM)), nCode);
+                         CPLToupper(static_cast<unsigned char>(*pszEM)), nCode);
 
             break;
         }
diff --git a/ogr/ogrsf_frmts/avc/avc_binwr.cpp b/ogr/ogrsf_frmts/avc/avc_binwr.cpp
index 2e7828179d32..5febe68bc65a 100644
--- a/ogr/ogrsf_frmts/avc/avc_binwr.cpp
+++ b/ogr/ogrsf_frmts/avc/avc_binwr.cpp
@@ -1793,7 +1793,8 @@ AVCBinFile *AVCBinWriteCreateTable(const char *pszInfoPath,
         for (i = 0; *pszPtr != '\0' && *pszPtr != '.' && *pszPtr != ' ';
              i++, pszPtr++)
         {
-            szCoverName[i] = (char)tolower(static_cast<unsigned char>(*pszPtr));
+            szCoverName[i] =
+                (char)CPLTolower(static_cast<unsigned char>(*pszPtr));
         }
         szCoverName[i] = '\0';
 
@@ -1802,13 +1803,14 @@ AVCBinFile *AVCBinWriteCreateTable(const char *pszInfoPath,
 
         for (i = 0; i < 3 && *pszPtr != '\0' && *pszPtr != ' '; i++, pszPtr++)
         {
-            szExt[i] = (char)tolower(static_cast<unsigned char>(*pszPtr));
+            szExt[i] = (char)CPLTolower(static_cast<unsigned char>(*pszPtr));
         }
         szExt[i] = '\0';
 
         for (i = 0; *pszPtr != '\0' && *pszPtr != ' '; i++, pszPtr++)
         {
-            szSubclass[i] = (char)tolower(static_cast<unsigned char>(*pszPtr));
+            szSubclass[i] =
+                (char)CPLTolower(static_cast<unsigned char>(*pszPtr));
         }
         szSubclass[i] = '\0';
 
@@ -1980,7 +1982,7 @@ AVCBinFile *_AVCBinWriteCreateDBFTable(const char *pszPath,
          i++, pszDBFBasename++)
     {
         psFile->pszFilename[i] =
-            (char)tolower(static_cast<unsigned char>(*pszDBFBasename));
+            (char)CPLTolower(static_cast<unsigned char>(*pszDBFBasename));
     }
 
     strcat(psFile->pszFilename, ".dbf");
diff --git a/ogr/ogrsf_frmts/avc/avc_e00gen.cpp b/ogr/ogrsf_frmts/avc/avc_e00gen.cpp
index d0b848c1dd48..2d1b49d92064 100644
--- a/ogr/ogrsf_frmts/avc/avc_e00gen.cpp
+++ b/ogr/ogrsf_frmts/avc/avc_e00gen.cpp
@@ -169,7 +169,7 @@ const char *AVCE00GenStartSection(AVCE00GenInfo *psInfo, AVCFileType eType,
         for (i = 0; pszClassName[i] != '\0'; i++)
         {
             psInfo->pszBuf[i] =
-                (char)toupper(static_cast<unsigned char>(pszClassName[i]));
+                (char)CPLToupper(static_cast<unsigned char>(pszClassName[i]));
         }
         psInfo->pszBuf[i] = '\0';
     }
diff --git a/ogr/ogrsf_frmts/avc/avc_e00read.cpp b/ogr/ogrsf_frmts/avc/avc_e00read.cpp
index d397573412c8..255ac4ba05c6 100644
--- a/ogr/ogrsf_frmts/avc/avc_e00read.cpp
+++ b/ogr/ogrsf_frmts/avc/avc_e00read.cpp
@@ -1008,7 +1008,7 @@ static int _AVCE00ReadBuildSqueleton(AVCE00ReadPtr psInfo, char **papszCoverDir)
         CPLSPrintf("EXP  0 %s%s.E00", szCWD, osCoverPathTruncated.c_str()));
     pcTmp = pszEXPPath;
     for (; *pcTmp != '\0'; pcTmp++)
-        *pcTmp = (char)toupper(static_cast<unsigned char>(*pcTmp));
+        *pcTmp = (char)CPLToupper(static_cast<unsigned char>(*pcTmp));
 
     /*-----------------------------------------------------------------
      * EXP Header
@@ -1309,7 +1309,8 @@ static int _AVCE00ReadBuildSqueleton(AVCE00ReadPtr psInfo, char **papszCoverDir)
                                      papszCoverDir[iFile]);
                 pcTmp = (char *)szFname;
                 for (; *pcTmp != '\0'; pcTmp++)
-                    *pcTmp = (char)toupper(static_cast<unsigned char>(*pcTmp));
+                    *pcTmp =
+                        (char)CPLToupper(static_cast<unsigned char>(*pcTmp));
                 papszCoverDir[iFile][nLen - 4] = '.';
 
                 papszTables = CSLAddString(papszTables, szFname);
diff --git a/ogr/ogrsf_frmts/avc/avc_e00write.cpp b/ogr/ogrsf_frmts/avc/avc_e00write.cpp
index 789feddfa9fb..67f5578cc3a4 100644
--- a/ogr/ogrsf_frmts/avc/avc_e00write.cpp
+++ b/ogr/ogrsf_frmts/avc/avc_e00write.cpp
@@ -480,7 +480,8 @@ static void _AVCE00WriteRenameTable(AVCTableDef *psTableDef,
 
     snprintf(szNewName, sizeof(szNewName), "%s", pszNewCoverName);
     for (i = 0; szNewName[i] != '\0'; i++)
-        szNewName[i] = (char)toupper(static_cast<unsigned char>(szNewName[i]));
+        szNewName[i] =
+            (char)CPLToupper(static_cast<unsigned char>(szNewName[i]));
 
     /*-----------------------------------------------------------------
      * Extract components from the current table name.
@@ -662,7 +663,7 @@ static int _AVCE00WriteCreateCoverFile(AVCE00WritePtr psInfo, AVCFileType eType,
      * Make sure filename is all lowercase and attempt to create the file
      *----------------------------------------------------------------*/
     for (i = 0; szFname[i] != '\0'; i++)
-        szFname[i] = (char)tolower(static_cast<unsigned char>(szFname[i]));
+        szFname[i] = (char)CPLTolower(static_cast<unsigned char>(szFname[i]));
 
     if (nStatus == 0)
     {
@@ -961,8 +962,8 @@ int AVCE00DeleteCoverage(const char *pszCoverToDelete)
         {
             /* Convert table filename to lowercases */
             for (j = 0; papszFiles[i] && papszFiles[i][j] != '\0'; j++)
-                papszFiles[i][j] =
-                    (char)tolower(static_cast<unsigned char>(papszFiles[i][j]));
+                papszFiles[i][j] = (char)CPLTolower(
+                    static_cast<unsigned char>(papszFiles[i][j]));
 
             /* Delete the .DAT file */
             pszFname = CPLSPrintf("%s%s.dat", pszInfoPath, papszFiles[i]);
diff --git a/ogr/ogrsf_frmts/carto/ogrcartodatasource.cpp b/ogr/ogrsf_frmts/carto/ogrcartodatasource.cpp
index 3b8ca2da213f..a50ec0d778ac 100644
--- a/ogr/ogrsf_frmts/carto/ogrcartodatasource.cpp
+++ b/ogr/ogrsf_frmts/carto/ogrcartodatasource.cpp
@@ -458,7 +458,7 @@ OGRCARTODataSource::ICreateLayer(const char *pszNameIn,
     CPLString osName(pszNameIn);
     if (CPLFetchBool(papszOptions, "LAUNDER", true))
     {
-        char *pszTmp = OGRPGCommonLaunderName(pszNameIn);
+        char *pszTmp = OGRPGCommonLaunderName(pszNameIn, "CARTO", false);
         osName = pszTmp;
         CPLFree(pszTmp);
     }
diff --git a/ogr/ogrsf_frmts/carto/ogrcartotablelayer.cpp b/ogr/ogrsf_frmts/carto/ogrcartotablelayer.cpp
index 70d4275edf80..695632dcd17c 100644
--- a/ogr/ogrsf_frmts/carto/ogrcartotablelayer.cpp
+++ b/ogr/ogrsf_frmts/carto/ogrcartotablelayer.cpp
@@ -671,7 +671,7 @@ OGRCARTOTableLayer::CreateGeomField(const OGRGeomFieldDefn *poGeomFieldIn,
     if (bLaunderColumnNames)
     {
         char *pszSafeName =
-            OGRPGCommonLaunderName(poGeomField->GetNameRef(), "PG");
+            OGRPGCommonLaunderName(poGeomField->GetNameRef(), "CARTO", false);
         poGeomField->SetName(pszSafeName);
         CPLFree(pszSafeName);
     }
@@ -735,7 +735,8 @@ OGRErr OGRCARTOTableLayer::CreateField(const OGRFieldDefn *poFieldIn,
     OGRFieldDefn oField(poFieldIn);
     if (bLaunderColumnNames)
     {
-        char *pszName = OGRPGCommonLaunderName(oField.GetNameRef());
+        char *pszName =
+            OGRPGCommonLaunderName(oField.GetNameRef(), "CARTO", false);
         oField.SetName(pszName);
         CPLFree(pszName);
     }
diff --git a/ogr/ogrsf_frmts/dxf/ogr_autocad_services.cpp b/ogr/ogrsf_frmts/dxf/ogr_autocad_services.cpp
index cf19f856544e..7e37fbf2b9ec 100644
--- a/ogr/ogrsf_frmts/dxf/ogr_autocad_services.cpp
+++ b/ogr/ogrsf_frmts/dxf/ogr_autocad_services.cpp
@@ -67,7 +67,7 @@ CPLString ACTextUnescape(const char *pszRawInput, const char *pszEncoding,
             if (pszInput[1] == ' ')
                 osResult += '^';
             else
-                osResult += static_cast<char>(toupper(
+                osResult += static_cast<char>(CPLToupper(
                                 static_cast<unsigned char>(pszInput[1]))) ^
                             0x40;
             pszInput++;
diff --git a/ogr/ogrsf_frmts/edigeo/ogredigeodatasource.cpp b/ogr/ogrsf_frmts/edigeo/ogredigeodatasource.cpp
index aeda2eb0fd9a..d966bd15f764 100644
--- a/ogr/ogrsf_frmts/edigeo/ogredigeodatasource.cpp
+++ b/ogr/ogrsf_frmts/edigeo/ogredigeodatasource.cpp
@@ -188,10 +188,8 @@ VSILFILE *OGREDIGEODataSource::OpenFile(const char *pszType,
     VSILFILE *fp = VSIFOpenL(osFilename, "rb");
     if (fp == nullptr)
     {
-        CPLString osExtLower = osExt;
-        for (int i = 0; i < (int)osExt.size(); i++)
-            osExtLower[i] = (char)tolower(static_cast<unsigned char>(osExt[i]));
-        CPLString osFilename2 = CPLFormCIFilename(
+        const CPLString osExtLower = CPLString(osExt).tolower();
+        const CPLString osFilename2 = CPLFormCIFilename(
             CPLGetPath(pszName), osTmp.c_str(), osExtLower.c_str());
         fp = VSIFOpenL(osFilename2, "rb");
         if (fp == nullptr)
diff --git a/ogr/ogrsf_frmts/elastic/ogrelasticlayer.cpp b/ogr/ogrsf_frmts/elastic/ogrelasticlayer.cpp
index bb60c85390dc..ebfbdeea7799 100644
--- a/ogr/ogrsf_frmts/elastic/ogrelasticlayer.cpp
+++ b/ogr/ogrsf_frmts/elastic/ogrelasticlayer.cpp
@@ -1415,7 +1415,8 @@ static void decode_geohash_bbox(const char *geohash, double lat[2],
     hashlen = static_cast<int>(strlen(geohash));
     for (i = 0; i < hashlen; i++)
     {
-        c = static_cast<char>(tolower(static_cast<unsigned char>(geohash[i])));
+        c = static_cast<char>(
+            CPLTolower(static_cast<unsigned char>(geohash[i])));
         cd = static_cast<char>(strchr(BASE32, c) - BASE32);
         for (j = 0; j < 5; j++)
         {
diff --git a/ogr/ogrsf_frmts/gmlas/ogrgmlaslayer.cpp b/ogr/ogrsf_frmts/gmlas/ogrgmlaslayer.cpp
index 62c52eaba5bd..4635659c873c 100644
--- a/ogr/ogrsf_frmts/gmlas/ogrgmlaslayer.cpp
+++ b/ogr/ogrsf_frmts/gmlas/ogrgmlaslayer.cpp
@@ -1262,7 +1262,8 @@ CPLString OGRGMLASLayer::LaunderFieldName(const CPLString &osFieldName)
 
     if (m_poDS->GetConf().m_bPGIdentifierLaundering)
     {
-        char *pszLaundered = OGRPGCommonLaunderName(osLaunderedName, "GMLAS");
+        char *pszLaundered =
+            OGRPGCommonLaunderName(osLaunderedName, "GMLAS", false);
         osLaunderedName = pszLaundered;
         CPLFree(pszLaundered);
     }
diff --git a/ogr/ogrsf_frmts/gmlas/ogrgmlasschemaanalyzer.cpp b/ogr/ogrsf_frmts/gmlas/ogrgmlasschemaanalyzer.cpp
index cb7bd6c7aba6..ad5f3b6d4864 100644
--- a/ogr/ogrsf_frmts/gmlas/ogrgmlasschemaanalyzer.cpp
+++ b/ogr/ogrsf_frmts/gmlas/ogrgmlasschemaanalyzer.cpp
@@ -549,7 +549,7 @@ bool GMLASSchemaAnalyzer::LaunderFieldNames(GMLASFeatureClass &oClass)
         for (size_t i = 0; i < aoFields.size(); i++)
         {
             char *pszLaundered =
-                OGRPGCommonLaunderName(aoFields[i].GetName(), "GMLAS");
+                OGRPGCommonLaunderName(aoFields[i].GetName(), "GMLAS", false);
             aoFields[i].SetName(pszLaundered);
             CPLFree(pszLaundered);
         }
@@ -640,7 +640,7 @@ void GMLASSchemaAnalyzer::LaunderClassNames()
         for (size_t i = 0; i < aoClasses.size(); i++)
         {
             char *pszLaundered =
-                OGRPGCommonLaunderName(aoClasses[i]->GetName(), "GMLAS");
+                OGRPGCommonLaunderName(aoClasses[i]->GetName(), "GMLAS", false);
             aoClasses[i]->SetName(pszLaundered);
             CPLFree(pszLaundered);
         }
diff --git a/ogr/ogrsf_frmts/gmlas/ogrgmlasutils.cpp b/ogr/ogrsf_frmts/gmlas/ogrgmlasutils.cpp
index 82f0de613598..910b98501417 100644
--- a/ogr/ogrsf_frmts/gmlas/ogrgmlasutils.cpp
+++ b/ogr/ogrsf_frmts/gmlas/ogrgmlasutils.cpp
@@ -52,8 +52,7 @@ CPLString OGRGMLASTruncateIdentifier(const CPLString &osName,
         const char *pszToken = papszTokens[j];
         bool bIsCamelCase = false;
         // Split parts like camelCase or CamelCase into several tokens
-        if (pszToken[0] != '\0' &&
-            islower(static_cast<unsigned char>(pszToken[1])))
+        if (pszToken[0] != '\0' && pszToken[1] >= 'a' && pszToken[1] <= 'z')
         {
             bIsCamelCase = true;
             bool bLastIsLower = true;
@@ -63,7 +62,7 @@ CPLString OGRGMLASTruncateIdentifier(const CPLString &osName,
             osCurrentPart += pszToken[1];
             for (int k = 2; pszToken[k]; ++k)
             {
-                if (isupper(static_cast<unsigned char>(pszToken[k])))
+                if (pszToken[k] >= 'A' && pszToken[k] <= 'Z')
                 {
                     if (!bLastIsLower)
                     {
diff --git a/ogr/ogrsf_frmts/gpkg/ogr_geopackage.h b/ogr/ogrsf_frmts/gpkg/ogr_geopackage.h
index 031cabcf565d..eeb300ce8d69 100644
--- a/ogr/ogrsf_frmts/gpkg/ogr_geopackage.h
+++ b/ogr/ogrsf_frmts/gpkg/ogr_geopackage.h
@@ -374,6 +374,8 @@ class GDALGeoPackageDataset final : public OGRSQLiteBaseDataSource,
         return nSoftTransactionLevel > 0;
     }
 
+    static std::string LaunderName(const std::string &osStr);
+
     // At least 100000 to avoid conflicting with EPSG codes
     static constexpr int FIRST_CUSTOM_SRSID = 100000;
 
@@ -707,6 +709,7 @@ class OGRGeoPackageTableLayer final : public OGRGeoPackageLayer
     bool m_bTruncateFields = false;
     bool m_bDeferredCreation = false;
     bool m_bTableCreatedInTransaction = false;
+    bool m_bLaunder = false;
     int m_iFIDAsRegularColumnIndex = -1;
     std::string m_osInsertionBuffer{};  // used by FeatureBindParameters to
                                         // store datetime values
@@ -977,6 +980,11 @@ class OGRGeoPackageTableLayer final : public OGRGeoPackageLayer
         m_bTruncateFields = CPL_TO_BOOL(bFlag);
     }
 
+    void SetLaunder(bool bFlag)
+    {
+        m_bLaunder = bFlag;
+    }
+
     OGRErr RunDeferredCreationIfNecessary();
     bool RunDeferredDropRTreeTableIfNecessary();
     bool DoJobAtTransactionCommit();
diff --git a/ogr/ogrsf_frmts/gpkg/ogrgeopackagedatasource.cpp b/ogr/ogrsf_frmts/gpkg/ogrgeopackagedatasource.cpp
index 9701755e14de..5d478837fc10 100644
--- a/ogr/ogrsf_frmts/gpkg/ogrgeopackagedatasource.cpp
+++ b/ogr/ogrsf_frmts/gpkg/ogrgeopackagedatasource.cpp
@@ -6660,6 +6660,72 @@ OGRLayer *GDALGeoPackageDataset::GetLayer(int iLayer)
         return m_papoLayers[iLayer];
 }
 
+/************************************************************************/
+/*                           LaunderName()                              */
+/************************************************************************/
+
+/** Launder identifiers (table, column names) according to guidance at
+ * https://www.geopackage.org/guidance/getting-started.html:
+ * "For maximum interoperability, start your database identifiers (table names,
+ * column names, etc.) with a lowercase character and only use lowercase
+ * characters, numbers 0-9, and underscores (_)."
+ */
+
+/* static */
+std::string GDALGeoPackageDataset::LaunderName(const std::string &osStr)
+{
+    char *pszASCII = CPLUTF8ForceToASCII(osStr.c_str(), '_');
+    const std::string osStrASCII(pszASCII);
+    CPLFree(pszASCII);
+
+    std::string osRet;
+    osRet.reserve(osStrASCII.size());
+
+    for (size_t i = 0; i < osStrASCII.size(); ++i)
+    {
+        if (osRet.empty())
+        {
+            if (osStrASCII[i] >= 'A' && osStrASCII[i] <= 'Z')
+            {
+                osRet += (osStrASCII[i] - 'A' + 'a');
+            }
+            else if (osStrASCII[i] >= 'a' && osStrASCII[i] <= 'z')
+            {
+                osRet += osStrASCII[i];
+            }
+            else
+            {
+                continue;
+            }
+        }
+        else if (osStrASCII[i] >= 'A' && osStrASCII[i] <= 'Z')
+        {
+            osRet += (osStrASCII[i] - 'A' + 'a');
+        }
+        else if ((osStrASCII[i] >= 'a' && osStrASCII[i] <= 'z') ||
+                 (osStrASCII[i] >= '0' && osStrASCII[i] <= '9') ||
+                 osStrASCII[i] == '_')
+        {
+            osRet += osStrASCII[i];
+        }
+        else
+        {
+            osRet += '_';
+        }
+    }
+
+    if (osRet.empty() && !osStrASCII.empty())
+        return LaunderName(std::string("x").append(osStrASCII));
+
+    if (osRet != osStr)
+    {
+        CPLDebug("PG", "LaunderName('%s') -> '%s'", osStr.c_str(),
+                 osRet.c_str());
+    }
+
+    return osRet;
+}
+
 /************************************************************************/
 /*                          ICreateLayer()                              */
 /************************************************************************/
@@ -6682,6 +6748,11 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
         return nullptr;
     }
 
+    const bool bLaunder =
+        CPLTestBool(CSLFetchNameValueDef(papszOptions, "LAUNDER", "NO"));
+    const std::string osTableName(bLaunder ? LaunderName(pszLayerName)
+                                           : std::string(pszLayerName));
+
     const auto eGType =
         poSrcGeomFieldDefn ? poSrcGeomFieldDefn->GetType() : wkbNone;
     const auto poSpatialRef =
@@ -6710,7 +6781,7 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
                 pszOtherIdentifier = m_papoLayers[i]->GetName();
             if (pszOtherIdentifier != nullptr &&
                 EQUAL(pszOtherIdentifier, pszIdentifier) &&
-                !EQUAL(m_papoLayers[i]->GetName(), pszLayerName))
+                !EQUAL(m_papoLayers[i]->GetName(), osTableName.c_str()))
             {
                 CPLError(CE_Failure, CPLE_AppDefined,
                          "Identifier %s is already used by table %s",
@@ -6729,7 +6800,7 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
         sqlite3_free(pszSQL);
         if (oResult && oResult->RowCount() > 0 &&
             oResult->GetValue(0, 0) != nullptr &&
-            !EQUAL(oResult->GetValue(0, 0), pszLayerName))
+            !EQUAL(oResult->GetValue(0, 0), osTableName.c_str()))
         {
             CPLError(CE_Failure, CPLE_AppDefined,
                      "Identifier %s is already used by table %s", pszIdentifier,
@@ -6772,7 +6843,7 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
 
         /* Avoiding gpkg prefixes is not an official requirement, but seems wise
          */
-        if (STARTS_WITH(pszLayerName, "gpkg"))
+        if (STARTS_WITH(osTableName.c_str(), "gpkg"))
         {
             CPLError(CE_Failure, CPLE_AppDefined,
                      "The layer name may not begin with 'gpkg' as it is a "
@@ -6782,7 +6853,8 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
 
         /* Preemptively try and avoid sqlite3 syntax errors due to  */
         /* illegal characters. */
-        if (strspn(pszLayerName, "`~!@#$%^&*()+-={}|[]\\:\";'<>?,./") > 0)
+        if (strspn(osTableName.c_str(), "`~!@#$%^&*()+-={}|[]\\:\";'<>?,./") >
+            0)
         {
             CPLError(
                 CE_Failure, CPLE_AppDefined,
@@ -6794,7 +6866,7 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
     /* Check for any existing layers that already use this name */
     for (int iLayer = 0; iLayer < m_nLayers; iLayer++)
     {
-        if (EQUAL(pszLayerName, m_papoLayers[iLayer]->GetName()))
+        if (EQUAL(osTableName.c_str(), m_papoLayers[iLayer]->GetName()))
         {
             const char *pszOverwrite =
                 CSLFetchNameValue(papszOptions, "OVERWRITE");
@@ -6808,7 +6880,7 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
                          "Layer %s already exists, CreateLayer failed.\n"
                          "Use the layer creation option OVERWRITE=YES to "
                          "replace it.",
-                         pszLayerName);
+                         osTableName.c_str());
                 return nullptr;
             }
         }
@@ -6824,7 +6896,7 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
 
     /* Create a blank layer. */
     auto poLayer = std::unique_ptr<OGRGeoPackageTableLayer>(
-        new OGRGeoPackageTableLayer(this, pszLayerName));
+        new OGRGeoPackageTableLayer(this, osTableName.c_str()));
 
     OGRSpatialReference *poSRS = nullptr;
     if (poSpatialRef)
@@ -6833,7 +6905,9 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
         poSRS->SetAxisMappingStrategy(OAMS_TRADITIONAL_GIS_ORDER);
     }
     poLayer->SetCreationParameters(
-        eGType, pszGeomColumnName, bGeomNullable, poSRS,
+        eGType,
+        bLaunder ? LaunderName(pszGeomColumnName).c_str() : pszGeomColumnName,
+        bGeomNullable, poSRS,
         CSLFetchNameValue(papszOptions, "SRID"),
         poSrcGeomFieldDefn ? poSrcGeomFieldDefn->GetCoordinatePrecision()
                            : OGRGeomCoordinatePrecision(),
@@ -6841,13 +6915,15 @@ GDALGeoPackageDataset::ICreateLayer(const char *pszLayerName,
             CSLFetchNameValueDef(papszOptions, "DISCARD_COORD_LSB", "NO")),
         CPLTestBool(CSLFetchNameValueDef(
             papszOptions, "UNDO_DISCARD_COORD_LSB_ON_READING", "NO")),
-        pszFIDColumnName, pszIdentifier,
-        CSLFetchNameValue(papszOptions, "DESCRIPTION"));
+        bLaunder ? LaunderName(pszFIDColumnName).c_str() : pszFIDColumnName,
+        pszIdentifier, CSLFetchNameValue(papszOptions, "DESCRIPTION"));
     if (poSRS)
     {
         poSRS->Release();
     }
 
+    poLayer->SetLaunder(bLaunder);
+
     /* Should we create a spatial index ? */
     const char *pszSI = CSLFetchNameValue(papszOptions, "SPATIAL_INDEX");
     int bCreateSpatialIndex = (pszSI == nullptr || CPLTestBool(pszSI));
diff --git a/ogr/ogrsf_frmts/gpkg/ogrgeopackagedriver.cpp b/ogr/ogrsf_frmts/gpkg/ogrgeopackagedriver.cpp
index 5ff549b492ac..a6111fd8dd6b 100644
--- a/ogr/ogrsf_frmts/gpkg/ogrgeopackagedriver.cpp
+++ b/ogr/ogrsf_frmts/gpkg/ogrgeopackagedriver.cpp
@@ -670,6 +670,8 @@ void RegisterOGRGeoPackage()
     poDriver->SetMetadataItem(
         GDAL_DS_LAYER_CREATIONOPTIONLIST,
         "<LayerCreationOptionList>"
+        "  <Option name='LAUNDER' type='boolean' description='Whether layer "
+        "and field names will be laundered.' default='NO'/>"
         "  <Option name='GEOMETRY_NAME' type='string' description='Name of "
         "geometry column.' default='geom' deprecated_alias='GEOMETRY_COLUMN'/>"
         "  <Option name='GEOMETRY_NULLABLE' type='boolean' "
diff --git a/ogr/ogrsf_frmts/gpkg/ogrgeopackagetablelayer.cpp b/ogr/ogrsf_frmts/gpkg/ogrgeopackagetablelayer.cpp
index 5fc36cc05699..f66297252c74 100644
--- a/ogr/ogrsf_frmts/gpkg/ogrgeopackagetablelayer.cpp
+++ b/ogr/ogrsf_frmts/gpkg/ogrgeopackagetablelayer.cpp
@@ -1740,8 +1740,13 @@ OGRErr OGRGeoPackageTableLayer::CreateField(const OGRFieldDefn *poField,
         oFieldDefn.SetWidth(0);
     oFieldDefn.SetPrecision(0);
 
+    if (m_bLaunder)
+        oFieldDefn.SetName(
+            GDALGeoPackageDataset::LaunderName(oFieldDefn.GetNameRef())
+                .c_str());
+
     if (m_pszFidColumn != nullptr &&
-        EQUAL(poField->GetNameRef(), m_pszFidColumn) &&
+        EQUAL(oFieldDefn.GetNameRef(), m_pszFidColumn) &&
         poField->GetType() != OFTInteger &&
         poField->GetType() != OFTInteger64 &&
         // typically a GeoPackage exported with QGIS as a shapefile and
@@ -1750,7 +1755,7 @@ OGRErr OGRGeoPackageTableLayer::CreateField(const OGRFieldDefn *poField,
           poField->GetPrecision() == 0))
     {
         CPLError(CE_Failure, CPLE_AppDefined, "Wrong field type for %s",
-                 poField->GetNameRef());
+                 oFieldDefn.GetNameRef());
         return OGRERR_FAILURE;
     }
 
@@ -1763,7 +1768,7 @@ OGRErr OGRGeoPackageTableLayer::CreateField(const OGRFieldDefn *poField,
 
         osCommand.Printf("ALTER TABLE \"%s\" ADD COLUMN \"%s\" %s",
                          SQLEscapeName(m_pszTableName).c_str(),
-                         SQLEscapeName(poField->GetNameRef()).c_str(),
+                         SQLEscapeName(oFieldDefn.GetNameRef()).c_str(),
                          GPkgFieldFromOGR(poField->GetType(),
                                           poField->GetSubType(), nMaxWidth));
         if (!poField->IsNullable())
diff --git a/ogr/ogrsf_frmts/hana/ogrhanadatasource.cpp b/ogr/ogrsf_frmts/hana/ogrhanadatasource.cpp
index 8527bbebfc34..bb1c698eaefe 100644
--- a/ogr/ogrsf_frmts/hana/ogrhanadatasource.cpp
+++ b/ogr/ogrsf_frmts/hana/ogrhanadatasource.cpp
@@ -367,8 +367,8 @@ GetGeometryColumnDescription(odbc::Connection &conn, const CPLString &query,
             columnName.end(),
             [](char ch1, char ch2)
             {
-                return std::toupper(static_cast<unsigned char>(ch1)) ==
-                       std::toupper(static_cast<unsigned char>(ch2));
+                return CPLToupper(static_cast<unsigned char>(ch1)) ==
+                       CPLToupper(static_cast<unsigned char>(ch2));
             });
 
         if (it != preparedQuery.end())
@@ -1285,8 +1285,8 @@ std::pair<OGRErr, CPLString> OGRHanaDataSource::LaunderName(const char *name)
             if (c == '-' || c == '#')
                 newName[i] = '_';
             else
-                newName[i] =
-                    static_cast<char>(toupper(static_cast<unsigned char>(c)));
+                newName[i] = static_cast<char>(
+                    CPLToupper(static_cast<unsigned char>(c)));
         }
         else
         {
diff --git a/ogr/ogrsf_frmts/ili/ili2reader.cpp b/ogr/ogrsf_frmts/ili/ili2reader.cpp
index 0b343b9ebb8d..577c06217572 100644
--- a/ogr/ogrsf_frmts/ili/ili2reader.cpp
+++ b/ogr/ogrsf_frmts/ili/ili2reader.cpp
@@ -72,10 +72,10 @@ int cmpStr(const string &s1, const string &s2)
 
     while (p1 != s1.end() && p2 != s2.end())
     {
-        if (toupper(static_cast<unsigned char>(*p1)) !=
-            toupper(static_cast<unsigned char>(*p2)))
-            return (toupper(static_cast<unsigned char>(*p1)) <
-                    toupper(static_cast<unsigned char>(*p2)))
+        if (CPLToupper(static_cast<unsigned char>(*p1)) !=
+            CPLToupper(static_cast<unsigned char>(*p2)))
+            return (CPLToupper(static_cast<unsigned char>(*p1)) <
+                    CPLToupper(static_cast<unsigned char>(*p2)))
                        ? -1
                        : 1;
         ++p1;
diff --git a/ogr/ogrsf_frmts/mitab/mitab_feature.cpp b/ogr/ogrsf_frmts/mitab/mitab_feature.cpp
index b79679cff706..4145fb265a39 100644
--- a/ogr/ogrsf_frmts/mitab/mitab_feature.cpp
+++ b/ogr/ogrsf_frmts/mitab/mitab_feature.cpp
@@ -1820,7 +1820,7 @@ const char *TABCustomPoint::GetSymbolStyleString(double dfAngle) const
     for (i = 0; i < 7 && *pszPtr != '\0' && *pszPtr != ' '; i++, pszPtr++)
     {
         szLowerExt[i] =
-            static_cast<char>(tolower(static_cast<unsigned char>(*pszPtr)));
+            static_cast<char>(CPLTolower(static_cast<unsigned char>(*pszPtr)));
     }
     szLowerExt[i] = '\0';
 
@@ -6314,7 +6314,7 @@ const char *TABText::GetLabelStyleString() const
         for (int i = 0; pszTextString[i]; ++i)
             if (isalpha(static_cast<unsigned char>(pszTextString[i])))
                 pszTextString[i] = static_cast<char>(
-                    toupper(static_cast<unsigned char>(pszTextString[i])));
+                    CPLToupper(static_cast<unsigned char>(pszTextString[i])));
 
     /* Escape the double quote chars and expand the text */
     char *pszTmpTextString = nullptr;
diff --git a/ogr/ogrsf_frmts/mitab/mitab_indfile.cpp b/ogr/ogrsf_frmts/mitab/mitab_indfile.cpp
index 165c08f31185..b270897639b6 100644
--- a/ogr/ogrsf_frmts/mitab/mitab_indfile.cpp
+++ b/ogr/ogrsf_frmts/mitab/mitab_indfile.cpp
@@ -599,8 +599,8 @@ GByte *TABINDFile::BuildKey(int nIndexNumber, const char *pszStr)
     int i = 0;
     for (i = 0; i < nKeyLength && pszStr[i] != '\0'; i++)
     {
-        m_papbyKeyBuffers[nIndexNumber - 1][i] =
-            static_cast<GByte>(toupper(static_cast<unsigned char>(pszStr[i])));
+        m_papbyKeyBuffers[nIndexNumber - 1][i] = static_cast<GByte>(
+            CPLToupper(static_cast<unsigned char>(pszStr[i])));
     }
 
     /* Pad the end of the buffer with '\0' */
diff --git a/ogr/ogrsf_frmts/mitab/mitab_utils.cpp b/ogr/ogrsf_frmts/mitab/mitab_utils.cpp
index 3d9d62f80b53..ffb2d3ba70ba 100644
--- a/ogr/ogrsf_frmts/mitab/mitab_utils.cpp
+++ b/ogr/ogrsf_frmts/mitab/mitab_utils.cpp
@@ -240,8 +240,8 @@ GBool TABAdjustFilenameExtension(char *pszFname)
     for (int i = static_cast<int>(strlen(pszFname)) - 1;
          i >= 0 && pszFname[i] != '.'; i--)
     {
-        pszFname[i] =
-            static_cast<char>(toupper(static_cast<unsigned char>(pszFname[i])));
+        pszFname[i] = static_cast<char>(
+            CPLToupper(static_cast<unsigned char>(pszFname[i])));
     }
 
     if (VSIStatL(pszFname, &sStatBuf) == 0)
@@ -253,8 +253,8 @@ GBool TABAdjustFilenameExtension(char *pszFname)
     for (int i = static_cast<int>(strlen(pszFname)) - 1;
          i >= 0 && pszFname[i] != '.'; i--)
     {
-        pszFname[i] =
-            static_cast<char>(tolower(static_cast<unsigned char>(pszFname[i])));
+        pszFname[i] = static_cast<char>(
+            CPLTolower(static_cast<unsigned char>(pszFname[i])));
     }
 
     if (VSIStatL(pszFname, &sStatBuf) == 0)
diff --git a/ogr/ogrsf_frmts/mssqlspatial/ogrmssqlspatialdatasource.cpp b/ogr/ogrsf_frmts/mssqlspatial/ogrmssqlspatialdatasource.cpp
index 4e64615e77ad..215080cbc260 100644
--- a/ogr/ogrsf_frmts/mssqlspatial/ogrmssqlspatialdatasource.cpp
+++ b/ogr/ogrsf_frmts/mssqlspatial/ogrmssqlspatialdatasource.cpp
@@ -1357,7 +1357,7 @@ char *OGRMSSQLSpatialDataSource::LaunderName(const char *pszSrcName)
     for (i = 0; pszSafeName[i] != '\0'; i++)
     {
         pszSafeName[i] =
-            (char)tolower(static_cast<unsigned char>(pszSafeName[i]));
+            (char)CPLTolower(static_cast<unsigned char>(pszSafeName[i]));
         if (pszSafeName[i] == '-' || pszSafeName[i] == '#')
             pszSafeName[i] = '_';
     }
diff --git a/ogr/ogrsf_frmts/mysql/ogrmysqldatasource.cpp b/ogr/ogrsf_frmts/mysql/ogrmysqldatasource.cpp
index 09636fb357d3..041a777f739a 100644
--- a/ogr/ogrsf_frmts/mysql/ogrmysqldatasource.cpp
+++ b/ogr/ogrsf_frmts/mysql/ogrmysqldatasource.cpp
@@ -1068,7 +1068,7 @@ char *OGRMySQLDataSource::LaunderName(const char *pszSrcName)
     for (int i = 0; pszSafeName[i] != '\0'; i++)
     {
         pszSafeName[i] =
-            (char)tolower(static_cast<unsigned char>(pszSafeName[i]));
+            (char)CPLTolower(static_cast<unsigned char>(pszSafeName[i]));
         if (pszSafeName[i] == '-' || pszSafeName[i] == '#')
             pszSafeName[i] = '_';
     }
diff --git a/ogr/ogrsf_frmts/oci/ogrocisession.cpp b/ogr/ogrsf_frmts/oci/ogrocisession.cpp
index 8de280a93c90..26ec7fb4b755 100644
--- a/ogr/ogrsf_frmts/oci/ogrocisession.cpp
+++ b/ogr/ogrsf_frmts/oci/ogrocisession.cpp
@@ -560,8 +560,8 @@ void OGROCISession::CleanName(char *pszName)
 
     for (i = 0; pszName[i] != '\0'; i++)
     {
-        pszName[i] =
-            static_cast<char>(toupper(static_cast<unsigned char>(pszName[i])));
+        pszName[i] = static_cast<char>(
+            CPLToupper(static_cast<unsigned char>(pszName[i])));
 
         if ((pszName[i] < '0' || pszName[i] > '9') &&
             (pszName[i] < 'A' || pszName[i] > 'Z') && pszName[i] != '_')
diff --git a/ogr/ogrsf_frmts/pg/ogr_pg.h b/ogr/ogrsf_frmts/pg/ogr_pg.h
index 40e9e0981388..2bd57b53b475 100644
--- a/ogr/ogrsf_frmts/pg/ogr_pg.h
+++ b/ogr/ogrsf_frmts/pg/ogr_pg.h
@@ -324,6 +324,7 @@ class OGRPGTableLayer final : public OGRPGLayer
     CPLString osWHERE{};
 
     int bLaunderColumnNames = true;
+    bool m_bUTF8ToASCII = false;
     int bPreservePrecision = true;
     int bUseCopy = USE_COPY_UNSET;
     int bCopyActive = false;
@@ -465,6 +466,11 @@ class OGRPGTableLayer final : public OGRPGLayer
         bLaunderColumnNames = bFlag;
     }
 
+    void SetUTF8ToASCIIFlag(bool bFlag)
+    {
+        m_bUTF8ToASCII = bFlag;
+    }
+
     void SetPrecisionFlag(int bFlag)
     {
         bPreservePrecision = bFlag;
diff --git a/ogr/ogrsf_frmts/pg/ogrpgdatasource.cpp b/ogr/ogrsf_frmts/pg/ogrpgdatasource.cpp
index c72621599036..e86973fbfb2a 100644
--- a/ogr/ogrsf_frmts/pg/ogrpgdatasource.cpp
+++ b/ogr/ogrsf_frmts/pg/ogrpgdatasource.cpp
@@ -1525,7 +1525,10 @@ OGRLayer *OGRPGDataSource::ICreateLayer(const char *pszLayerName,
 
     EndCopy();
 
-    const bool bLaunder = CPLFetchBool(papszOptions, "LAUNDER", true);
+    const bool bUTF8ToASCII =
+        CPLFetchBool(papszOptions, "LAUNDER_ASCII", false);
+    const bool bLaunder =
+        bUTF8ToASCII || CPLFetchBool(papszOptions, "LAUNDER", true);
 
     const char *pszFIDColumnNameIn = CSLFetchNameValue(papszOptions, "FID");
     CPLString osFIDColumnName;
@@ -1536,7 +1539,7 @@ OGRLayer *OGRPGDataSource::ICreateLayer(const char *pszLayerName,
         if (bLaunder)
         {
             char *pszLaunderedFid =
-                OGRPGCommonLaunderName(pszFIDColumnNameIn, "PG");
+                OGRPGCommonLaunderName(pszFIDColumnNameIn, "PG", bUTF8ToASCII);
             osFIDColumnName += pszLaunderedFid;
             CPLFree(pszLaunderedFid);
         }
@@ -1612,8 +1615,8 @@ OGRLayer *OGRPGDataSource::ICreateLayer(const char *pszLayerName,
         pszSchemaName[length] = '\0';
 
         if (bLaunder)
-            pszTableName =
-                OGRPGCommonLaunderName(pszDotPos + 1, "PG");  // skip "."
+            pszTableName = OGRPGCommonLaunderName(pszDotPos + 1, "PG",
+                                                  bUTF8ToASCII);  // skip "."
         else
             pszTableName = CPLStrdup(pszDotPos + 1);  // skip "."
     }
@@ -1621,8 +1624,8 @@ OGRLayer *OGRPGDataSource::ICreateLayer(const char *pszLayerName,
     {
         pszSchemaName = nullptr;
         if (bLaunder)
-            pszTableName =
-                OGRPGCommonLaunderName(pszLayerName, "PG");  // skip "."
+            pszTableName = OGRPGCommonLaunderName(pszLayerName, "PG",
+                                                  bUTF8ToASCII);  // skip "."
         else
             pszTableName = CPLStrdup(pszLayerName);  // skip "."
     }
@@ -2024,6 +2027,7 @@ OGRLayer *OGRPGDataSource::ICreateLayer(const char *pszLayerName,
     poLayer->SetTableDefinition(osFIDColumnName, pszGFldName, eType,
                                 pszGeomType, nSRSId, GeometryTypeFlags);
     poLayer->SetLaunderFlag(bLaunder);
+    poLayer->SetUTF8ToASCIIFlag(bUTF8ToASCII);
     poLayer->SetPrecisionFlag(CPLFetchBool(papszOptions, "PRECISION", true));
     // poLayer->SetForcedSRSId(nForcedSRSId);
     poLayer->SetForcedGeometryTypeFlags(ForcedGeometryTypeFlags);
diff --git a/ogr/ogrsf_frmts/pg/ogrpgdrivercore.cpp b/ogr/ogrsf_frmts/pg/ogrpgdrivercore.cpp
index 0670ae6f35fc..f8d2216bf125 100644
--- a/ogr/ogrsf_frmts/pg/ogrpgdrivercore.cpp
+++ b/ogr/ogrsf_frmts/pg/ogrpgdrivercore.cpp
@@ -112,6 +112,8 @@ void OGRPGDriverSetCommonMetadata(GDALDriver *poDriver)
         "default='NO'/>"
         "  <Option name='LAUNDER' type='boolean' description='Whether layer "
         "and field names will be laundered' default='YES'/>"
+        "  <Option name='LAUNDER_ASCII' type='boolean' description='Same as "
+        "LAUNDER, but force generation of ASCII identifiers' default='NO'/>"
         "  <Option name='PRECISION' type='boolean' description='Whether fields "
         "created should keep the width and precision' default='YES'/>"
         "  <Option name='DIM' type='string' description='Set to 2 to force the "
diff --git a/ogr/ogrsf_frmts/pg/ogrpgtablelayer.cpp b/ogr/ogrsf_frmts/pg/ogrpgtablelayer.cpp
index 99c8f81cdd75..973e8286ff43 100644
--- a/ogr/ogrsf_frmts/pg/ogrpgtablelayer.cpp
+++ b/ogr/ogrsf_frmts/pg/ogrpgtablelayer.cpp
@@ -2370,7 +2370,8 @@ OGRErr OGRPGTableLayer::CreateField(const OGRFieldDefn *poFieldIn,
     /* -------------------------------------------------------------------- */
     if (bLaunderColumnNames)
     {
-        char *pszSafeName = OGRPGCommonLaunderName(oField.GetNameRef(), "PG");
+        char *pszSafeName =
+            OGRPGCommonLaunderName(oField.GetNameRef(), "PG", m_bUTF8ToASCII);
 
         oField.SetName(pszSafeName);
         CPLFree(pszSafeName);
@@ -2634,8 +2635,8 @@ OGRErr OGRPGTableLayer::CreateGeomField(const OGRGeomFieldDefn *poGeomFieldIn,
     /* -------------------------------------------------------------------- */
     if (bLaunderColumnNames)
     {
-        char *pszSafeName =
-            OGRPGCommonLaunderName(poGeomField->GetNameRef(), "PG");
+        char *pszSafeName = OGRPGCommonLaunderName(poGeomField->GetNameRef(),
+                                                   "PG", m_bUTF8ToASCII);
 
         poGeomField->SetName(pszSafeName);
         CPLFree(pszSafeName);
@@ -2961,8 +2962,8 @@ OGRErr OGRPGTableLayer::AlterFieldDefn(int iField, OGRFieldDefn *poNewFieldDefn,
     {
         if (bLaunderColumnNames)
         {
-            char *pszSafeName =
-                OGRPGCommonLaunderName(oField.GetNameRef(), "PG");
+            char *pszSafeName = OGRPGCommonLaunderName(oField.GetNameRef(),
+                                                       "PG", m_bUTF8ToASCII);
             oField.SetName(pszSafeName);
             CPLFree(pszSafeName);
         }
diff --git a/ogr/ogrsf_frmts/pgdump/ogr_pgdump.h b/ogr/ogrsf_frmts/pgdump/ogr_pgdump.h
index 068101ad29d7..910f99404486 100644
--- a/ogr/ogrsf_frmts/pgdump/ogr_pgdump.h
+++ b/ogr/ogrsf_frmts/pgdump/ogr_pgdump.h
@@ -69,7 +69,8 @@ void CPL_DLL OGRPGCommonAppendFieldValue(
     OGRPGCommonEscapeStringCbk pfnEscapeString, void *userdata);
 
 char CPL_DLL *OGRPGCommonLaunderName(const char *pszSrcName,
-                                     const char *pszDebugPrefix = "OGR");
+                                     const char *pszDebugPrefix,
+                                     bool bUTF8ToASCII);
 
 /************************************************************************/
 /*                        OGRPGDumpGeomFieldDefn                        */
@@ -110,6 +111,7 @@ class OGRPGDumpLayer final : public OGRLayer
     OGRFeatureDefn *m_poFeatureDefn = nullptr;
     OGRPGDumpDataSource *m_poDS = nullptr;
     bool m_bLaunderColumnNames = true;
+    bool m_bUTF8ToASCII = false;
     bool m_bPreservePrecision = true;
     int m_bUseCopy = USE_COPY_UNSET;
     bool m_bWriteAsHex = false;
@@ -191,6 +193,11 @@ class OGRPGDumpLayer final : public OGRLayer
         m_bLaunderColumnNames = bFlag;
     }
 
+    void SetUTF8ToASCIIFlag(bool bFlag)
+    {
+        m_bUTF8ToASCII = bFlag;
+    }
+
     void SetPrecisionFlag(bool bFlag)
     {
         m_bPreservePrecision = bFlag;
diff --git a/ogr/ogrsf_frmts/pgdump/ogrpgdumpdatasource.cpp b/ogr/ogrsf_frmts/pgdump/ogrpgdumpdatasource.cpp
index 50c5da7e2378..b4edaafd5756 100644
--- a/ogr/ogrsf_frmts/pgdump/ogrpgdumpdatasource.cpp
+++ b/ogr/ogrsf_frmts/pgdump/ogrpgdumpdatasource.cpp
@@ -127,27 +127,32 @@ void OGRPGDumpDataSource::LogCommit()
 /*                         OGRPGCommonLaunderName()                     */
 /************************************************************************/
 
-char *OGRPGCommonLaunderName(const char *pszSrcName, const char *pszDebugPrefix)
+char *OGRPGCommonLaunderName(const char *pszSrcName, const char *pszDebugPrefix,
+                             bool bUTF8ToASCII)
 
 {
-    char *pszSafeName = CPLStrdup(pszSrcName);
+    char *pszSafeName = bUTF8ToASCII ? CPLUTF8ForceToASCII(pszSrcName, '_')
+                                     : CPLStrdup(pszSrcName);
 
     int i = 0;  // needed after loop
     for (; i < OGR_PG_NAMEDATALEN - 1 && pszSafeName[i] != '\0'; i++)
     {
-        pszSafeName[i] =
-            (char)tolower(static_cast<unsigned char>(pszSafeName[i]));
-        if (pszSafeName[i] == '\'' || pszSafeName[i] == '-' ||
-            pszSafeName[i] == '#')
+        if (static_cast<unsigned char>(pszSafeName[i]) <= 127)
         {
-            pszSafeName[i] = '_';
+            pszSafeName[i] =
+                (char)CPLTolower(static_cast<unsigned char>(pszSafeName[i]));
+            if (pszSafeName[i] == '\'' || pszSafeName[i] == '-' ||
+                pszSafeName[i] == '#')
+            {
+                pszSafeName[i] = '_';
+            }
         }
     }
     pszSafeName[i] = '\0';
 
     if (strcmp(pszSrcName, pszSafeName) != 0)
     {
-        if (strlen(pszSafeName) < strlen(pszSrcName))
+        if (CPLStrlenUTF8(pszSafeName) < CPLStrlenUTF8(pszSrcName))
         {
             CPLError(CE_Warning, CPLE_AppDefined,
                      "%s identifier truncated to %s", pszSrcName, pszSafeName);
@@ -250,7 +255,10 @@ OGRPGDumpDataSource::ICreateLayer(const char *pszLayerName,
     const char *pszDotPos = strstr(pszLayerName, ".");
     std::string osTable;
     std::string osSchema;
-    const bool bLaunder = CPLFetchBool(papszOptions, "LAUNDER", true);
+    const bool bUTF8ToASCII =
+        CPLFetchBool(papszOptions, "LAUNDER_ASCII", false);
+    const bool bLaunder =
+        bUTF8ToASCII || CPLFetchBool(papszOptions, "LAUNDER", true);
 
     if (pszDotPos != nullptr && bExtractSchemaFromLayerName)
     {
@@ -260,8 +268,8 @@ OGRPGDumpDataSource::ICreateLayer(const char *pszLayerName,
 
         if (bLaunder)
         {
-            char *pszTmp =
-                OGRPGCommonLaunderName(pszDotPos + 1, "PGDump");  // skip "."
+            char *pszTmp = OGRPGCommonLaunderName(pszDotPos + 1, "PGDump",
+                                                  bUTF8ToASCII);  // skip "."
             osTable = pszTmp;
             CPLFree(pszTmp);
         }
@@ -272,7 +280,8 @@ OGRPGDumpDataSource::ICreateLayer(const char *pszLayerName,
     {
         if (bLaunder)
         {
-            char *pszTmp = OGRPGCommonLaunderName(pszLayerName, "PGDump");
+            char *pszTmp =
+                OGRPGCommonLaunderName(pszLayerName, "PGDump", bUTF8ToASCII);
             osTable = pszTmp;
             CPLFree(pszTmp);
         }
@@ -470,8 +479,8 @@ OGRPGDumpDataSource::ICreateLayer(const char *pszLayerName,
     {
         if (bLaunder)
         {
-            char *pszLaunderedFid =
-                OGRPGCommonLaunderName(pszFIDColumnNameIn, "PGDump");
+            char *pszLaunderedFid = OGRPGCommonLaunderName(
+                pszFIDColumnNameIn, "PGDump", bUTF8ToASCII);
             osFIDColumnName = pszLaunderedFid;
             CPLFree(pszLaunderedFid);
         }
@@ -622,6 +631,7 @@ OGRPGDumpDataSource::ICreateLayer(const char *pszLayerName,
         !osFIDColumnName.empty() ? osFIDColumnName.c_str() : nullptr,
         bWriteAsHex, bCreateTable);
     poLayer->SetLaunderFlag(bLaunder);
+    poLayer->SetUTF8ToASCIIFlag(bUTF8ToASCII);
     poLayer->SetPrecisionFlag(CPLFetchBool(papszOptions, "PRECISION", true));
 
     const char *pszOverrideColumnTypes =
diff --git a/ogr/ogrsf_frmts/pgdump/ogrpgdumpdriver.cpp b/ogr/ogrsf_frmts/pgdump/ogrpgdumpdriver.cpp
index b82cd9980fc0..d519ef9a60b7 100644
--- a/ogr/ogrsf_frmts/pgdump/ogrpgdumpdriver.cpp
+++ b/ogr/ogrsf_frmts/pgdump/ogrpgdumpdriver.cpp
@@ -99,6 +99,8 @@ void RegisterOGRPGDump()
         "  </Option>"
         "  <Option name='LAUNDER' type='boolean' description='Whether layer "
         "and field names will be laundered' default='YES'/>"
+        "  <Option name='LAUNDER_ASCII' type='boolean' description='Same as "
+        "LAUNDER, but force generation of ASCII identifiers' default='NO'/>"
         "  <Option name='PRECISION' type='boolean' description='Whether fields "
         "created should keep the width and precision' default='YES'/>"
         "  <Option name='DIM' type='string' description='Set to 2 to force the "
diff --git a/ogr/ogrsf_frmts/pgdump/ogrpgdumplayer.cpp b/ogr/ogrsf_frmts/pgdump/ogrpgdumplayer.cpp
index e636aa78cad9..e8d07f811445 100644
--- a/ogr/ogrsf_frmts/pgdump/ogrpgdumplayer.cpp
+++ b/ogr/ogrsf_frmts/pgdump/ogrpgdumplayer.cpp
@@ -1592,8 +1592,8 @@ OGRErr OGRPGDumpLayer::CreateField(const OGRFieldDefn *poFieldIn, int bApproxOK)
     /* -------------------------------------------------------------------- */
     if (m_bLaunderColumnNames)
     {
-        char *pszSafeName =
-            OGRPGCommonLaunderName(oField.GetNameRef(), "PGDump");
+        char *pszSafeName = OGRPGCommonLaunderName(oField.GetNameRef(),
+                                                   "PGDump", m_bUTF8ToASCII);
 
         oField.SetName(pszSafeName);
         CPLFree(pszSafeName);
@@ -1719,8 +1719,8 @@ OGRErr OGRPGDumpLayer::CreateGeomField(const OGRGeomFieldDefn *poGeomFieldIn,
     /* -------------------------------------------------------------------- */
     if (m_bLaunderColumnNames)
     {
-        char *pszSafeName =
-            OGRPGCommonLaunderName(poGeomField->GetNameRef(), "PGDump");
+        char *pszSafeName = OGRPGCommonLaunderName(poGeomField->GetNameRef(),
+                                                   "PGDump", m_bUTF8ToASCII);
 
         poGeomField->SetName(pszSafeName);
         CPLFree(pszSafeName);
diff --git a/ogr/ogrsf_frmts/sqlite/ogrsqlitedatasource.cpp b/ogr/ogrsf_frmts/sqlite/ogrsqlitedatasource.cpp
index ae4584f3bb11..f936fa05ebfb 100644
--- a/ogr/ogrsf_frmts/sqlite/ogrsqlitedatasource.cpp
+++ b/ogr/ogrsf_frmts/sqlite/ogrsqlitedatasource.cpp
@@ -3746,7 +3746,7 @@ char *OGRSQLiteDataSource::LaunderName(const char *pszSrcName)
     for (int i = 0; pszSafeName[i] != '\0'; i++)
     {
         pszSafeName[i] =
-            (char)tolower(static_cast<unsigned char>(pszSafeName[i]));
+            (char)CPLTolower(static_cast<unsigned char>(pszSafeName[i]));
         if (pszSafeName[i] == '\'' || pszSafeName[i] == '-' ||
             pszSafeName[i] == '#')
             pszSafeName[i] = '_';
diff --git a/ogr/swq_op_general.cpp b/ogr/swq_op_general.cpp
index b8e250ed6f54..89e3bb4209fa 100644
--- a/ogr/swq_op_general.cpp
+++ b/ogr/swq_op_general.cpp
@@ -157,8 +157,8 @@ int swq_test_like(const char *input, const char *pattern, char chEscape,
             }
             else if ((!insensitive && *pattern != *input) ||
                      (insensitive &&
-                      tolower(static_cast<unsigned char>(*pattern)) !=
-                          tolower(static_cast<unsigned char>(*input))))
+                      CPLTolower(static_cast<unsigned char>(*pattern)) !=
+                          CPLTolower(static_cast<unsigned char>(*input))))
             {
                 return 0;
             }
diff --git a/port/cpl_conv.cpp b/port/cpl_conv.cpp
index 6779baf4a79c..afcfd3eac95e 100644
--- a/port/cpl_conv.cpp
+++ b/port/cpl_conv.cpp
@@ -327,7 +327,7 @@ char *CPLStrdup(const char *pszString)
  * Convert each characters of the string to lower case.
  *
  * For example, "ABcdE" will be converted to "abcde".
- * This function is locale dependent.
+ * Starting with GDAL 3.9, this function is no longer locale dependent.
  *
  * @param pszString input string to be converted.
  * @return pointer to the same string, pszString.
@@ -344,7 +344,7 @@ char *CPLStrlwr(char *pszString)
     while (*pszTemp)
     {
         *pszTemp =
-            static_cast<char>(tolower(static_cast<unsigned char>(*pszTemp)));
+            static_cast<char>(CPLTolower(static_cast<unsigned char>(*pszTemp)));
         pszTemp++;
     }
 
diff --git a/port/cpl_path.cpp b/port/cpl_path.cpp
index ec5efeaca505..f78c77453bef 100644
--- a/port/cpl_path.cpp
+++ b/port/cpl_path.cpp
@@ -654,8 +654,7 @@ const char *CPLFormCIFilename(const char *pszPath, const char *pszBasename,
     {
         for (size_t i = 0; pszFilename[i] != '\0'; i++)
         {
-            if (islower(static_cast<unsigned char>(pszFilename[i])))
-                pszFilename[i] = static_cast<char>(toupper(pszFilename[i]));
+            pszFilename[i] = static_cast<char>(CPLToupper(pszFilename[i]));
         }
 
         pszFullPath = CPLFormFilename(pszPath, pszFilename, nullptr);
@@ -666,9 +665,8 @@ const char *CPLFormCIFilename(const char *pszPath, const char *pszBasename,
     {
         for (size_t i = 0; pszFilename[i] != '\0'; i++)
         {
-            if (isupper(static_cast<unsigned char>(pszFilename[i])))
-                pszFilename[i] = static_cast<char>(
-                    tolower(static_cast<unsigned char>(pszFilename[i])));
+            pszFilename[i] = static_cast<char>(
+                CPLTolower(static_cast<unsigned char>(pszFilename[i])));
         }
 
         pszFullPath = CPLFormFilename(pszPath, pszFilename, nullptr);
diff --git a/port/cpl_recode.cpp b/port/cpl_recode.cpp
index c438fb8f76f5..9d881070e804 100644
--- a/port/cpl_recode.cpp
+++ b/port/cpl_recode.cpp
@@ -30,6 +30,8 @@
 
 #include "cpl_conv.h"
 
+#include "utf8.h"
+
 #ifdef CPL_RECODE_ICONV
 extern void CPLClearRecodeIconvWarningFlags();
 extern char *CPLRecodeIconv(const char *, const char *,
@@ -294,6 +296,11 @@ bool CPLIsASCII(const char *pabyData, size_t nLen)
  * characters are found in the input string, they will be replaced by the
  * provided replacement character.
  *
+ * This function does not make any assumption on the encoding of the input
+ * string (except it must be nul-terminated if nLen equals -1, or have at
+ * least nLen bytes otherwise). CPLUTF8ForceToASCII() can be used instead when
+ * the input string is known to be UTF-8 encoded.
+ *
  * @param pabyData input string to test
  * @param nLen length of the input string, or -1 if the function must compute
  *             the string length. In which case it must be null terminated.
@@ -305,21 +312,798 @@ bool CPLIsASCII(const char *pabyData, size_t nLen)
  *
  * @since GDAL 1.7.0
  */
-char CPL_DLL *CPLForceToASCII(const char *pabyData, int nLen,
-                              char chReplacementChar)
+char *CPLForceToASCII(const char *pabyData, int nLen, char chReplacementChar)
 {
-    if (nLen < 0)
-        nLen = static_cast<int>(strlen(pabyData));
-    char *pszOutputString = static_cast<char *>(CPLMalloc(nLen + 1));
-    for (int i = 0; i < nLen; i++)
+    const size_t nRealLen =
+        (nLen >= 0) ? static_cast<size_t>(nLen) : strlen(pabyData);
+    char *pszOutputString = static_cast<char *>(CPLMalloc(nRealLen + 1));
+    const char *pszPtr = pabyData;
+    const char *pszEnd = pabyData + nRealLen;
+    size_t i = 0;
+    while (pszPtr != pszEnd)
     {
-        if (reinterpret_cast<unsigned char *>(const_cast<char *>(pabyData))[i] >
-            127)
+        if (*reinterpret_cast<const unsigned char *>(pszPtr) > 127)
+        {
             pszOutputString[i] = chReplacementChar;
+            ++pszPtr;
+            ++i;
+        }
         else
-            pszOutputString[i] = pabyData[i];
+        {
+            pszOutputString[i] = *pszPtr;
+            ++pszPtr;
+            ++i;
+        }
+    }
+    pszOutputString[i] = '\0';
+    return pszOutputString;
+}
+
+/************************************************************************/
+/*                       CPLUTF8ForceToASCII()                          */
+/************************************************************************/
+
+/**
+ * Return a new string that is made only of ASCII characters. If non-ASCII
+ * characters are found in the input string, for which an "equivalent" ASCII
+ * character is not found, they will be replaced by the provided replacement
+ * character.
+ *
+ * This function is aware of https://en.wikipedia.org/wiki/Latin-1_Supplement
+ * and https://en.wikipedia.org/wiki/Latin_Extended-A to provide sensible
+ * replacements for accented characters.
+
+ * @param pszStr NUL-terminated UTF-8 string.
+ * @param chReplacementChar character which will be used when the input stream
+ *                          contains a non ASCII character that cannot be
+ *                          substituted with an equivalent ASCII character.
+ *                          Must be valid ASCII!
+ *
+ * @return a new string that must be freed with CPLFree().
+ *
+ * @since GDAL 3.9
+ */
+char *CPLUTF8ForceToASCII(const char *pszStr, char chReplacementChar)
+{
+    static const struct
+    {
+        short nCodePoint;
+        char chFirst;
+        char chSecond;
+    } aLatinCharacters[] = {
+        // https://en.wikipedia.org/wiki/Latin-1_Supplement
+        {0xC0, 'A', 0},    // Latin Capital Letter A with grave
+        {0xC1, 'A', 0},    // Latin Capital letter A with acute
+        {0xC2, 'A', 0},    // Latin Capital letter A with circumflex
+        {0xC3, 'A', 0},    // Latin Capital letter A with tilde
+        {0xC4, 'A', 0},    // Latin Capital letter A with diaeresis
+        {0xC5, 'A', 0},    // Latin Capital letter A with ring above
+        {0xC6, 'A', 'E'},  // Latin Capital letter AE
+        {0xC7, 'C', 0},    // Latin Capital letter C with cedilla
+        {0xC8, 'E', 0},    // Latin Capital letter E with grave
+        {0xC9, 'E', 0},    // Latin Capital letter E with acute
+        {0xCA, 'E', 0},    // Latin Capital letter E with circumflex
+        {0xCB, 'E', 0},    // Latin Capital letter E with diaeresis
+        {0xCC, 'I', 0},    // Latin Capital letter I with grave
+        {0xCD, 'I', 0},    // Latin Capital letter I with acute
+        {0xCE, 'I', 0},    // Latin Capital letter I with circumflex
+        {0xCF, 'I', 0},    // Latin Capital letter I with diaeresis
+        // { 0xD0, '?', 0 }, // Latin Capital letter Eth
+        {0xD1, 'N', 0},  // Latin Capital letter N with tilde
+        {0xD2, 'O', 0},  // Latin Capital letter O with grave
+        {0xD3, 'O', 0},  // Latin Capital letter O with acute
+        {0xD4, 'O', 0},  // Latin Capital letter O with circumflex
+        {0xD5, 'O', 0},  // Latin Capital letter O with tilde
+        {0xD6, 'O', 0},  // Latin Capital letter O with diaeresis
+        {0xD8, 'O', 0},  // Latin Capital letter O with stroke
+        {0xD9, 'U', 0},  // Latin Capital letter U with grave
+        {0xDA, 'U', 0},  // Latin Capital letter U with acute
+        {0xDB, 'U', 0},  // Latin Capital Letter U with circumflex
+        {0xDC, 'U', 0},  // Latin Capital Letter U with diaeresis
+        {0xDD, 'Y', 0},  // Latin Capital Letter Y with acute
+        // { 0xDE, '?', 0 }, // Latin Capital Letter Thorn
+        {0xDF, 'S', 'S'},  // Latin Small Letter sharp S
+        {0xE0, 'a', 0},    // Latin Small Letter A with grave
+        {0xE1, 'a', 0},    // Latin Small Letter A with acute
+        {0xE2, 'a', 0},    // Latin Small Letter A with circumflex
+        {0xE3, 'a', 0},    // Latin Small Letter A with tilde
+        {0xE4, 'a', 0},    // Latin Small Letter A with diaeresis
+        {0xE5, 'a', 0},    // Latin Small Letter A with ring above
+        {0xE6, 'a', 'e'},  // Latin Small Letter AE
+        {0xE7, 'c', 0},    // Latin Small Letter C with cedilla
+        {0xE8, 'e', 0},    // Latin Small Letter E with grave
+        {0xE9, 'e', 0},    // Latin Small Letter E with acute
+        {0xEA, 'e', 0},    // Latin Small Letter E with circumflex
+        {0xEB, 'e', 0},    // Latin Small Letter E with diaeresis
+        {0xEC, 'i', 0},    // Latin Small Letter I with grave
+        {0xED, 'i', 0},    // Latin Small Letter I with acute
+        {0xEE, 'i', 0},    // Latin Small Letter I with circumflex
+        {0xEF, 'i', 0},    // Latin Small Letter I with diaeresis
+        // { 0xF0, '?', 0 }, // Latin Small Letter Eth
+        {0xF1, 'n', 0},  // Latin Small Letter N with tilde
+        {0xF2, 'o', 0},  // Latin Small Letter O with grave
+        {0xF3, 'o', 0},  // Latin Small Letter O with acute
+        {0xF4, 'o', 0},  // Latin Small Letter O with circumflex
+        {0xF5, 'o', 0},  // Latin Small Letter O with tilde
+        {0xF6, 'o', 0},  // Latin Small Letter O with diaeresis
+        {0xF8, 'o', 0},  // Latin Small Letter O with stroke
+        {0xF9, 'u', 0},  // Latin Small Letter U with grave
+        {0xFA, 'u', 0},  // Latin Small Letter U with acute
+        {0xFB, 'u', 0},  // Latin Small Letter U with circumflex
+        {0xFC, 'u', 0},  // Latin Small Letter U with diaeresis
+        {0xFD, 'y', 0},  // Latin Small Letter Y with acute
+        // { 0xFE, '?', 0 }, // Latin Small Letter Thorn
+        {0xFF, 'u', 0},  // Latin Small Letter Y with diaeresis
+
+        // https://en.wikipedia.org/wiki/Latin_Extended-A
+        {
+            0x0100,
+            'A',
+            0,
+        },  // Latin Capital letter A with macron
+        {
+            0x0101,
+            'a',
+            0,
+        },  // Latin Small letter A with macron
+        {
+            0x0102,
+            'A',
+            0,
+        },  // Latin Capital letter A with breve
+        {
+            0x0103,
+            'a',
+            0,
+        },  // Latin Small letter A with breve
+        {
+            0x0104,
+            'A',
+            0,
+        },  // Latin Capital letter A with ogonek
+        {
+            0x0105,
+            'a',
+            0,
+        },  // Latin Small letter A with ogonek
+        {
+            0x0106,
+            'C',
+            0,
+        },  // Latin Capital letter C with acute
+        {
+            0x0107,
+            'c',
+            0,
+        },  // Latin Small letter C with acute
+        {
+            0x0108,
+            'C',
+            0,
+        },  // Latin Capital letter C with circumflex
+        {
+            0x0109,
+            'c',
+            0,
+        },  // Latin Small letter C with circumflex
+        {
+            0x010A,
+            'C',
+            0,
+        },  // Latin Capital letter C with dot above
+        {
+            0x010B,
+            'c',
+            0,
+        },  // Latin Small letter C with dot above
+        {
+            0x010C,
+            'C',
+            0,
+        },  // Latin Capital letter C with caron
+        {
+            0x010D,
+            'c',
+            0,
+        },  // Latin Small letter C with caron
+        {
+            0x010E,
+            'D',
+            0,
+        },  // Latin Capital letter D with caron
+        {
+            0x010F,
+            'd',
+            0,
+        },  // Latin Small letter D with caron
+        {
+            0x0110,
+            'D',
+            0,
+        },  // Latin Capital letter D with stroke
+        {
+            0x0111,
+            'd',
+            0,
+        },  // Latin Small letter D with stroke
+        {
+            0x0112,
+            'E',
+            0,
+        },  // Latin Capital letter E with macron
+        {
+            0x0113,
+            'e',
+            0,
+        },  // Latin Small letter E with macron
+        {
+            0x0114,
+            'E',
+            0,
+        },  // Latin Capital letter E with breve
+        {
+            0x0115,
+            'e',
+            0,
+        },  // Latin Small letter E with breve
+        {
+            0x0116,
+            'E',
+            0,
+        },  // Latin Capital letter E with dot above
+        {
+            0x0117,
+            'e',
+            0,
+        },  // Latin Small letter E with dot above
+        {
+            0x0118,
+            'E',
+            0,
+        },  // Latin Capital letter E with ogonek
+        {
+            0x0119,
+            'e',
+            0,
+        },  // Latin Small letter E with ogonek
+        {
+            0x011A,
+            'E',
+            0,
+        },  // Latin Capital letter E with caron
+        {
+            0x011B,
+            'e',
+            0,
+        },  // Latin Small letter E with caron
+        {
+            0x011C,
+            'G',
+            0,
+        },  // Latin Capital letter G with circumflex
+        {
+            0x011D,
+            'g',
+            0,
+        },  // Latin Small letter G with circumflex
+        {
+            0x011E,
+            'G',
+            0,
+        },  // Latin Capital letter G with breve
+        {
+            0x011F,
+            'g',
+            0,
+        },  // Latin Small letter G with breve
+        {
+            0x0120,
+            'G',
+            0,
+        },  // Latin Capital letter G with dot above
+        {
+            0x0121,
+            'g',
+            0,
+        },  // Latin Small letter G with dot above
+        {
+            0x0122,
+            'G',
+            0,
+        },  // Latin Capital letter G with cedilla
+        {
+            0x0123,
+            'g',
+            0,
+        },  // Latin Small letter G with cedilla
+        {
+            0x0124,
+            'H',
+            0,
+        },  // Latin Capital letter H with circumflex
+        {
+            0x0125,
+            'h',
+            0,
+        },  // Latin Small letter H with circumflex
+        {
+            0x0126,
+            'H',
+            0,
+        },  // Latin Capital letter H with stroke
+        {
+            0x0127,
+            'h',
+            0,
+        },  // Latin Small letter H with stroke
+        {
+            0x0128,
+            'I',
+            0,
+        },  // Latin Capital letter I with tilde
+        {
+            0x0129,
+            'i',
+            0,
+        },  // Latin Small letter I with tilde
+        {
+            0x012A,
+            'I',
+            0,
+        },  // Latin Capital letter I with macron
+        {
+            0x012B,
+            'i',
+            0,
+        },  // Latin Small letter I with macron
+        {
+            0x012C,
+            'I',
+            0,
+        },  // Latin Capital letter I with breve
+        {
+            0x012D,
+            'i',
+            0,
+        },  // Latin Small letter I with breve
+        {
+            0x012E,
+            'I',
+            0,
+        },  // Latin Capital letter I with ogonek
+        {
+            0x012F,
+            'i',
+            0,
+        },  // Latin Small letter I with ogonek
+        {
+            0x0130,
+            'I',
+            0,
+        },  // Latin Capital letter I with dot above
+        {
+            0x0131,
+            'i',
+            0,
+        },  // Latin Small letter dotless I
+        {
+            0x0132,
+            'I',
+            'J',
+        },  // Latin Capital Ligature IJ
+        {
+            0x0133,
+            'i',
+            'j',
+        },  // Latin Small Ligature IJ
+        {
+            0x0134,
+            'J',
+            0,
+        },  // Latin Capital letter J with circumflex
+        {
+            0x0135,
+            'j',
+            0,
+        },  // Latin Small letter J with circumflex
+        {
+            0x0136,
+            'K',
+            0,
+        },  // Latin Capital letter K with cedilla
+        {
+            0x0137,
+            'k',
+            0,
+        },  // Latin Small letter K with cedilla
+        {
+            0x0138,
+            'k',
+            0,
+        },  // Latin Small letter Kra
+        {
+            0x0139,
+            'L',
+            0,
+        },  // Latin Capital letter L with acute
+        {
+            0x013A,
+            'l',
+            0,
+        },  // Latin Small letter L with acute
+        {
+            0x013B,
+            'L',
+            0,
+        },  // Latin Capital letter L with cedilla
+        {
+            0x013C,
+            'l',
+            0,
+        },  // Latin Small letter L with cedilla
+        {
+            0x013D,
+            'L',
+            0,
+        },  // Latin Capital letter L with caron
+        {
+            0x013E,
+            'l',
+            0,
+        },  // Latin Small letter L with caron
+        {
+            0x013F,
+            'L',
+            0,
+        },  // Latin Capital letter L with middle dot
+        {
+            0x0140,
+            'l',
+            0,
+        },  // Latin Small letter L with middle dot
+        {
+            0x0141,
+            'L',
+            0,
+        },  // Latin Capital letter L with stroke
+        {
+            0x0142,
+            'l',
+            0,
+        },  // Latin Small letter L with stroke
+        {
+            0x0143,
+            'N',
+            0,
+        },  // Latin Capital letter N with acute
+        {
+            0x0144,
+            'n',
+            0,
+        },  // Latin Small letter N with acute
+        {
+            0x0145,
+            'N',
+            0,
+        },  // Latin Capital letter N with cedilla
+        {
+            0x0146,
+            'n',
+            0,
+        },  // Latin Small letter N with cedilla
+        {
+            0x0147,
+            'N',
+            0,
+        },  // Latin Capital letter N with caron
+        {
+            0x0148,
+            'n',
+            0,
+        },  // Latin Small letter N with caron
+        // { 0x014A , '?' , 0, }, // Latin Capital letter Eng
+        // { 0x014B , '?' , 0, }, // Latin Small letter Eng
+        {
+            0x014C,
+            'O',
+            0,
+        },  // Latin Capital letter O with macron
+        {
+            0x014D,
+            'o',
+            0,
+        },  // Latin Small letter O with macron
+        {
+            0x014E,
+            'O',
+            0,
+        },  // Latin Capital letter O with breve
+        {
+            0x014F,
+            'o',
+            0,
+        },  // Latin Small letter O with breve
+        {
+            0x0150,
+            'O',
+            0,
+        },  // Latin Capital Letter O with double acute
+        {
+            0x0151,
+            'o',
+            0,
+        },  // Latin Small Letter O with double acute
+        {
+            0x0152,
+            'O',
+            'E',
+        },  // Latin Capital Ligature OE
+        {
+            0x0153,
+            'o',
+            'e',
+        },  // Latin Small Ligature OE
+        {
+            0x0154,
+            'R',
+            0,
+        },  // Latin Capital letter R with acute
+        {
+            0x0155,
+            'r',
+            0,
+        },  // Latin Small letter R with acute
+        {
+            0x0156,
+            'R',
+            0,
+        },  // Latin Capital letter R with cedilla
+        {
+            0x0157,
+            'r',
+            0,
+        },  // Latin Small letter R with cedilla
+        {
+            0x0158,
+            'R',
+            0,
+        },  // Latin Capital letter R with caron
+        {
+            0x0159,
+            'r',
+            0,
+        },  // Latin Small letter R with caron
+        {
+            0x015A,
+            'S',
+            0,
+        },  // Latin Capital letter S with acute
+        {
+            0x015B,
+            's',
+            0,
+        },  // Latin Small letter S with acute
+        {
+            0x015C,
+            'S',
+            0,
+        },  // Latin Capital letter S with circumflex
+        {
+            0x015D,
+            's',
+            0,
+        },  // Latin Small letter S with circumflex
+        {
+            0x015E,
+            'S',
+            0,
+        },  // Latin Capital letter S with cedilla
+        {
+            0x015F,
+            's',
+            0,
+        },  // Latin Small letter S with cedilla
+        {
+            0x0160,
+            'S',
+            0,
+        },  // Latin Capital letter S with caron
+        {
+            0x0161,
+            's',
+            0,
+        },  // Latin Small letter S with caron
+        {
+            0x0162,
+            'T',
+            0,
+        },  // Latin Capital letter T with cedilla
+        {
+            0x0163,
+            't',
+            0,
+        },  // Latin Small letter T with cedilla
+        {
+            0x0164,
+            'T',
+            0,
+        },  // Latin Capital letter T with caron
+        {
+            0x0165,
+            't',
+            0,
+        },  // Latin Small letter T with caron
+        {
+            0x0166,
+            'T',
+            0,
+        },  // Latin Capital letter T with stroke
+        {
+            0x0167,
+            't',
+            0,
+        },  // Latin Small letter T with stroke
+        {
+            0x0168,
+            'U',
+            0,
+        },  // Latin Capital letter U with tilde
+        {
+            0x0169,
+            'u',
+            0,
+        },  // Latin Small letter U with tilde
+        {
+            0x016A,
+            'U',
+            0,
+        },  // Latin Capital letter U with macron
+        {
+            0x016B,
+            'u',
+            0,
+        },  // Latin Small letter U with macron
+        {
+            0x016C,
+            'U',
+            0,
+        },  // Latin Capital letter U with breve
+        {
+            0x016D,
+            'u',
+            0,
+        },  // Latin Small letter U with breve
+        {
+            0x016E,
+            'U',
+            0,
+        },  // Latin Capital letter U with ring above
+        {
+            0x016F,
+            'u',
+            0,
+        },  // Latin Small letter U with ring above
+        {
+            0x0170,
+            'U',
+            0,
+        },  // Latin Capital Letter U with double acute
+        {
+            0x0171,
+            'u',
+            0,
+        },  // Latin Small Letter U with double acute
+        {
+            0x0172,
+            'U',
+            0,
+        },  // Latin Capital letter U with ogonek
+        {
+            0x0173,
+            'u',
+            0,
+        },  // Latin Small letter U with ogonek
+        {
+            0x0174,
+            'W',
+            0,
+        },  // Latin Capital letter W with circumflex
+        {
+            0x0175,
+            'w',
+            0,
+        },  // Latin Small letter W with circumflex
+        {
+            0x0176,
+            'Y',
+            0,
+        },  // Latin Capital letter Y with circumflex
+        {
+            0x0177,
+            'y',
+            0,
+        },  // Latin Small letter Y with circumflex
+        {
+            0x0178,
+            'Y',
+            0,
+        },  // Latin Capital letter Y with diaeresis
+        {
+            0x0179,
+            'Z',
+            0,
+        },  // Latin Capital letter Z with acute
+        {
+            0x017A,
+            'z',
+            0,
+        },  // Latin Small letter Z with acute
+        {
+            0x017B,
+            'Z',
+            0,
+        },  // Latin Capital letter Z with dot above
+        {
+            0x017C,
+            'z',
+            0,
+        },  // Latin Small letter Z with dot above
+        {
+            0x017D,
+            'Z',
+            0,
+        },  // Latin Capital letter Z with caron
+        {
+            0x017E,
+            'z',
+            0,
+        },  // Latin Small letter Z with caron
+    };
+
+    const size_t nLen = strlen(pszStr);
+    char *pszOutputString = static_cast<char *>(CPLMalloc(nLen + 1));
+    const char *pszPtr = pszStr;
+    const char *pszEnd = pszStr + nLen;
+    size_t i = 0;
+    while (pszPtr != pszEnd)
+    {
+        if (*reinterpret_cast<const unsigned char *>(pszPtr) > 127)
+        {
+            utf8_int32_t codepoint;
+            if (pszPtr + utf8codepointcalcsize(pszPtr) > pszEnd)
+                break;
+            auto pszNext = utf8codepoint(pszPtr, &codepoint);
+            char ch = chReplacementChar;
+            for (const auto &latin1char : aLatinCharacters)
+            {
+                if (codepoint == latin1char.nCodePoint)
+                {
+                    pszOutputString[i] = latin1char.chFirst;
+                    ++i;
+                    if (latin1char.chSecond)
+                    {
+                        pszOutputString[i] = latin1char.chSecond;
+                        ++i;
+                    }
+                    ch = 0;
+                    break;
+                }
+            }
+            if (ch)
+            {
+                pszOutputString[i] = ch;
+                ++i;
+            }
+            pszPtr = pszNext;
+        }
+        else
+        {
+            pszOutputString[i] = *pszPtr;
+            ++pszPtr;
+            ++i;
+        }
     }
-    pszOutputString[nLen] = '\0';
+    pszOutputString[i] = '\0';
     return pszOutputString;
 }
 
diff --git a/port/cpl_string.cpp b/port/cpl_string.cpp
index bbdddb651063..f7372c29f7cd 100644
--- a/port/cpl_string.cpp
+++ b/port/cpl_string.cpp
@@ -3021,3 +3021,33 @@ char **CSLParseCommandLine(const char *pszCommandLine)
 {
     return CSLTokenizeString(pszCommandLine);
 }
+
+/************************************************************************/
+/*                              CPLToupper()                            */
+/************************************************************************/
+
+/** Converts a (ASCII) lowercase character to uppercase.
+ *
+ * Same as standard toupper(), except that it is not locale sensitive.
+ *
+ * @since GDAL 3.9
+ */
+int CPLToupper(int c)
+{
+    return (c >= 'a' && c <= 'z') ? (c - 'a' + 'A') : c;
+}
+
+/************************************************************************/
+/*                              CPLTolower()                            */
+/************************************************************************/
+
+/** Converts a (ASCII) uppercase character to lowercase.
+ *
+ * Same as standard tolower(), except that it is not locale sensitive.
+ *
+ * @since GDAL 3.9
+ */
+int CPLTolower(int c)
+{
+    return (c >= 'A' && c <= 'Z') ? (c - 'A' + 'a') : c;
+}
diff --git a/port/cpl_string.h b/port/cpl_string.h
index faf8a9e99e20..f666bab9ab2c 100644
--- a/port/cpl_string.h
+++ b/port/cpl_string.h
@@ -190,6 +190,9 @@ typedef enum
 
 CPLValueType CPL_DLL CPLGetValueType(const char *pszValue);
 
+int CPL_DLL CPLToupper(int c);
+int CPL_DLL CPLTolower(int c);
+
 size_t CPL_DLL CPLStrlcpy(char *pszDest, const char *pszSrc, size_t nDestSize);
 size_t CPL_DLL CPLStrlcat(char *pszDest, const char *pszSrc, size_t nDestSize);
 size_t CPL_DLL CPLStrnlen(const char *pszStr, size_t nMaxLen);
@@ -273,6 +276,8 @@ int CPL_DLL CPLIsUTF8(const char *pabyData, int nLen);
 bool CPL_DLL CPLIsASCII(const char *pabyData, size_t nLen);
 char CPL_DLL *CPLForceToASCII(const char *pabyData, int nLen,
                               char chReplacementChar) CPL_WARN_UNUSED_RESULT;
+char CPL_DLL *CPLUTF8ForceToASCII(const char *pszStr, char chReplacementChar)
+    CPL_WARN_UNUSED_RESULT;
 int CPL_DLL CPLStrlenUTF8(const char *pszUTF8Str);
 int CPL_DLL CPLCanRecode(const char *pszTestStr, const char *pszSrcEncoding,
                          const char *pszDstEncoding) CPL_WARN_UNUSED_RESULT;
diff --git a/port/cplstring.cpp b/port/cplstring.cpp
index 4928892ce86b..17bfe4174759 100644
--- a/port/cplstring.cpp
+++ b/port/cplstring.cpp
@@ -278,7 +278,7 @@ size_t CPLString::ifind(const char *s, size_t nPos) const
 {
     const char *pszHaystack = c_str();
     const char chFirst =
-        static_cast<char>(::tolower(static_cast<unsigned char>(s[0])));
+        static_cast<char>(CPLTolower(static_cast<unsigned char>(s[0])));
     const size_t nTargetLen = strlen(s);
 
     if (nPos > size())
@@ -288,7 +288,7 @@ size_t CPLString::ifind(const char *s, size_t nPos) const
 
     while (*pszHaystack != '\0')
     {
-        if (chFirst == ::tolower(static_cast<unsigned char>(*pszHaystack)))
+        if (chFirst == CPLTolower(static_cast<unsigned char>(*pszHaystack)))
         {
             if (EQUALN(pszHaystack, s, nTargetLen))
                 return nPos;
@@ -313,7 +313,7 @@ CPLString &CPLString::toupper()
 
 {
     for (size_t i = 0; i < size(); i++)
-        (*this)[i] = static_cast<char>(::toupper((*this)[i]));
+        (*this)[i] = static_cast<char>(CPLToupper((*this)[i]));
 
     return *this;
 }
@@ -330,8 +330,7 @@ CPLString &CPLString::tolower()
 
 {
     for (size_t i = 0; i < size(); i++)
-        (*this)[i] = static_cast<char>(
-            ::tolower(static_cast<unsigned char>((*this)[i])));
+        (*this)[i] = static_cast<char>(CPLTolower((*this)[i]));
 
     return *this;
 }
diff --git a/ogr/utf8.h b/port/utf8.h
similarity index 100%
rename from ogr/utf8.h
rename to port/utf8.h