diff --git a/benchmark/buffers/buffer-iterate.js b/benchmark/buffers/buffer-iterate.js
index c1c4f6917501a1..44ea637a28e95a 100644
--- a/benchmark/buffers/buffer-iterate.js
+++ b/benchmark/buffers/buffer-iterate.js
@@ -1,11 +1,9 @@
 'use strict';
-const SlowBuffer = require('buffer').SlowBuffer;
 const common = require('../common.js');
 const assert = require('assert');
 
 const bench = common.createBenchmark(main, {
   size: [512, 4096, 16386],
-  type: ['fast'],
   method: ['for', 'forOf', 'iterator'],
   n: [1e3],
 });
@@ -16,10 +14,8 @@ const methods = {
   'iterator': benchIterator,
 };
 
-function main({ size, type, method, n }) {
-  const buffer = type === 'fast' ?
-    Buffer.alloc(size) :
-    SlowBuffer(size).fill(0);
+function main({ size, method, n }) {
+  const buffer = Buffer.alloc(size);
 
   const fn = methods[method];
 
diff --git a/benchmark/buffers/buffer-read-with-byteLength.js b/benchmark/buffers/buffer-read-with-byteLength.js
index 57e46b8ce4453f..bef09ce4f0d981 100644
--- a/benchmark/buffers/buffer-read-with-byteLength.js
+++ b/benchmark/buffers/buffer-read-with-byteLength.js
@@ -9,16 +9,13 @@ const types = [
 ];
 
 const bench = common.createBenchmark(main, {
-  buffer: ['fast'],
   type: types,
   n: [1e6],
   byteLength: [1, 2, 3, 4, 5, 6],
 });
 
-function main({ n, buf, type, byteLength }) {
-  const buff = buf === 'fast' ?
-    Buffer.alloc(8) :
-    require('buffer').SlowBuffer(8);
+function main({ n, type, byteLength }) {
+  const buff = Buffer.alloc(8);
   const fn = `read${type}`;
 
   buff.writeDoubleLE(0, 0);
diff --git a/benchmark/buffers/buffer-read.js b/benchmark/buffers/buffer-read.js
index f3b2a5645174fe..67892730ee71cc 100644
--- a/benchmark/buffers/buffer-read.js
+++ b/benchmark/buffers/buffer-read.js
@@ -19,15 +19,12 @@ const types = [
 ];
 
 const bench = common.createBenchmark(main, {
-  buffer: ['fast'],
   type: types,
   n: [1e6],
 });
 
-function main({ n, buf, type }) {
-  const buff = buf === 'fast' ?
-    Buffer.alloc(8) :
-    require('buffer').SlowBuffer(8);
+function main({ n, type }) {
+  const buff = Buffer.alloc(8);
   const fn = `read${type}`;
 
   buff.writeDoubleLE(0, 0);
diff --git a/benchmark/buffers/buffer-slice.js b/benchmark/buffers/buffer-slice.js
index cc6e1a8a1449fc..3b80c4d189fa06 100644
--- a/benchmark/buffers/buffer-slice.js
+++ b/benchmark/buffers/buffer-slice.js
@@ -1,17 +1,15 @@
 'use strict';
 const common = require('../common.js');
-const SlowBuffer = require('buffer').SlowBuffer;
 
 const bench = common.createBenchmark(main, {
-  type: ['fast', 'slow', 'subarray'],
+  type: ['slice', 'subarray'],
   n: [1e6],
 });
 
 const buf = Buffer.allocUnsafe(1024);
-const slowBuf = new SlowBuffer(1024);
 
 function main({ n, type }) {
-  const b = type === 'slow' ? slowBuf : buf;
+  const b = buf
   const fn = type === 'subarray' ?
     () => b.subarray(10, 256) :
     () => b.slice(10, 256);
diff --git a/benchmark/buffers/buffer-write.js b/benchmark/buffers/buffer-write.js
index 239abc8a0da69e..30475e484dd67d 100644
--- a/benchmark/buffers/buffer-write.js
+++ b/benchmark/buffers/buffer-write.js
@@ -27,7 +27,6 @@ const types = [
 ];
 
 const bench = common.createBenchmark(main, {
-  buffer: ['fast'],
   type: types,
   n: [1e6],
 });
@@ -70,10 +69,8 @@ const byteLength = {
   writeIntBE: 6,
 };
 
-function main({ n, buf, type }) {
-  const buff = buf === 'fast' ?
-    Buffer.alloc(8) :
-    require('buffer').SlowBuffer(8);
+function main({ n, type }) {
+  const buff = Buffer.alloc(8)
   const fn = `write${type}`;
 
   if (!/\d/.test(fn))
diff --git a/doc/api/buffer.md b/doc/api/buffer.md
index fbbcc04083ef51..dbd9520a846131 100644
--- a/doc/api/buffer.md
+++ b/doc/api/buffer.md
@@ -5326,30 +5326,6 @@ console.log(newBuf.toString('ascii'));
 Because the Euro (`€`) sign is not representable in US-ASCII, it is replaced
 with `?` in the transcoded `Buffer`.
 
-### Class: `SlowBuffer`
-
-<!-- YAML
-deprecated: v6.0.0
--->
-
-> Stability: 0 - Deprecated: Use [`Buffer.allocUnsafeSlow()`][] instead.
-
-See [`Buffer.allocUnsafeSlow()`][]. This was never a class in the sense that
-the constructor always returned a `Buffer` instance, rather than a `SlowBuffer`
-instance.
-
-#### `new SlowBuffer(size)`
-
-<!-- YAML
-deprecated: v6.0.0
--->
-
-> Stability: 0 - Deprecated: Use [`Buffer.allocUnsafeSlow()`][] instead.
-
-* `size` {integer} The desired length of the new `SlowBuffer`.
-
-See [`Buffer.allocUnsafeSlow()`][].
-
 ### Buffer constants
 
 <!-- YAML
@@ -5483,7 +5459,7 @@ added: v5.10.0
 Node.js can be started using the `--zero-fill-buffers` command-line option to
 cause all newly-allocated `Buffer` instances to be zero-filled upon creation by
 default. Without the option, buffers created with [`Buffer.allocUnsafe()`][],
-[`Buffer.allocUnsafeSlow()`][], and `new SlowBuffer(size)` are not zero-filled.
+and [`Buffer.allocUnsafeSlow()`][] are not zero-filled.
 Use of this flag can have a measurable negative impact on performance. Use the
 `--zero-fill-buffers` option only when necessary to enforce that newly allocated
 `Buffer` instances cannot contain old data that is potentially sensitive.
diff --git a/doc/api/cli.md b/doc/api/cli.md
index c33977a0b2be81..5bfcb1f133edf4 100644
--- a/doc/api/cli.md
+++ b/doc/api/cli.md
@@ -2833,8 +2833,7 @@ node --watch --watch-preserve-output test.js
 added: v6.0.0
 -->
 
-Automatically zero-fills all newly allocated [`Buffer`][] and [`SlowBuffer`][]
-instances.
+Automatically zero-fills all newly allocated [`Buffer`][] instances.
 
 ## Environment variables
 
@@ -3580,7 +3579,6 @@ node --stack-trace-limit=12 -p -e "Error.stackTraceLimit" # prints 12
 [`CRYPTO_secure_malloc_init`]: https://www.openssl.org/docs/man3.0/man3/CRYPTO_secure_malloc_init.html
 [`NODE_OPTIONS`]: #node_optionsoptions
 [`NO_COLOR`]: https://no-color.org
-[`SlowBuffer`]: buffer.md#class-slowbuffer
 [`Web Storage`]: https://developer.mozilla.org/en-US/docs/Web/API/Web_Storage_API
 [`WebSocket`]: https://developer.mozilla.org/en-US/docs/Web/API/WebSocket
 [`YoungGenerationSizeFromSemiSpaceSize`]: https://chromium.googlesource.com/v8/v8.git/+/refs/tags/10.3.129/src/heap/heap.cc#328
diff --git a/doc/api/deprecations.md b/doc/api/deprecations.md
index f10265b9ddd98a..49852acd1ad533 100644
--- a/doc/api/deprecations.md
+++ b/doc/api/deprecations.md
@@ -691,23 +691,6 @@ Type: End-of-Life
 
 `util.error()` has been removed. Please use [`console.error()`][] instead.
 
-### DEP0030: `SlowBuffer`
-
-<!-- YAML
-changes:
-  - version: v6.12.0
-    pr-url: https://github.com/nodejs/node/pull/10116
-    description: A deprecation code has been assigned.
-  - version: v6.0.0
-    pr-url: https://github.com/nodejs/node/pull/5833
-    description: Documentation-only deprecation.
--->
-
-Type: Documentation-only
-
-The [`SlowBuffer`][] class is deprecated. Please use
-[`Buffer.allocUnsafeSlow(size)`][] instead.
-
 ### DEP0031: `ecdh.setPublicKey()`
 
 <!-- YAML
@@ -3761,7 +3744,6 @@ It is recommended to use the `new` qualifier instead. This applies to all REPL c
 [`ReadStream.open()`]: fs.md#class-fsreadstream
 [`Server.getConnections()`]: net.md#servergetconnectionscallback
 [`Server.listen({fd: <number>})`]: net.md#serverlistenhandle-backlog-callback
-[`SlowBuffer`]: buffer.md#class-slowbuffer
 [`String.prototype.toWellFormed`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toWellFormed
 [`WriteStream.open()`]: fs.md#class-fswritestream
 [`assert.CallTracker`]: assert.md#class-assertcalltracker
diff --git a/doc/node.1 b/doc/node.1
index 2a8cd86433d7ed..76aaf00e14f357 100644
--- a/doc/node.1
+++ b/doc/node.1
@@ -609,7 +609,7 @@ If set to 0 then V8 will choose an appropriate size of the thread pool based on
 If the value provided is larger than V8's maximum, then the largest value will be chosen.
 .
 .It Fl -zero-fill-buffers
-Automatically zero-fills all newly allocated Buffer and SlowBuffer instances.
+Automatically zero-fills all newly allocated Buffer instances.
 .
 .It Fl c , Fl -check
 Check the script's syntax without executing it.
diff --git a/lib/buffer.js b/lib/buffer.js
index 6294eae2fb5093..4d50f15b14adc5 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -407,7 +407,7 @@ Buffer.allocUnsafe = function allocUnsafe(size) {
 };
 
 /**
- * Equivalent to SlowBuffer(num), by default creates a non-zero-filled
+ * By default creates a non-zero-filled
  * Buffer instance that is not allocated off the pre-initialized pool.
  * If `--zero-fill-buffers` is set, will zero-fill the buffer.
  */
@@ -416,16 +416,6 @@ Buffer.allocUnsafeSlow = function allocUnsafeSlow(size) {
   return createUnsafeBuffer(size);
 };
 
-// If --zero-fill-buffers command line argument is set, a zero-filled
-// buffer is returned.
-function SlowBuffer(size) {
-  validateNumber(size, 'size', 0, kMaxLength);
-  return createUnsafeBuffer(size);
-}
-
-ObjectSetPrototypeOf(SlowBuffer.prototype, Uint8ArrayPrototype);
-ObjectSetPrototypeOf(SlowBuffer, Uint8Array);
-
 function allocate(size) {
   if (size <= 0) {
     return new FastBuffer();
@@ -1322,7 +1312,6 @@ function isAscii(input) {
 
 module.exports = {
   Buffer,
-  SlowBuffer,
   transcode,
   isUtf8,
   isAscii,
diff --git a/src/node_options.cc b/src/node_options.cc
index 2ca6652538b30b..7c5195f4389a8c 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -978,8 +978,7 @@ PerProcessOptionsParser::PerProcessOptionsParser(
             &PerProcessOptions::v8_thread_pool_size,
             kAllowedInEnvvar);
   AddOption("--zero-fill-buffers",
-            "automatically zero-fill all newly allocated Buffer and "
-            "SlowBuffer instances",
+            "automatically zero-fill all newly allocated Buffer",
             &PerProcessOptions::zero_fill_all_buffers,
             kAllowedInEnvvar);
   AddOption("--debug-arraybuffer-allocations",
diff --git a/test/parallel/test-buffer-alloc.js b/test/parallel/test-buffer-alloc.js
index aad9c6bcab69e9..d053738f1ae410 100644
--- a/test/parallel/test-buffer-alloc.js
+++ b/test/parallel/test-buffer-alloc.js
@@ -5,7 +5,6 @@ const assert = require('assert');
 const vm = require('vm');
 
 const {
-  SlowBuffer,
   kMaxLength,
 } = require('buffer');
 
@@ -1104,8 +1103,6 @@ assert.throws(() => Buffer.from(null), {
 // Test prototype getters don't throw
 assert.strictEqual(Buffer.prototype.parent, undefined);
 assert.strictEqual(Buffer.prototype.offset, undefined);
-assert.strictEqual(SlowBuffer.prototype.parent, undefined);
-assert.strictEqual(SlowBuffer.prototype.offset, undefined);
 
 
 {
diff --git a/test/parallel/test-buffer-bytelength.js b/test/parallel/test-buffer-bytelength.js
index 95d54d425bc252..58d0efc7974438 100644
--- a/test/parallel/test-buffer-bytelength.js
+++ b/test/parallel/test-buffer-bytelength.js
@@ -2,7 +2,6 @@
 
 const common = require('../common');
 const assert = require('assert');
-const SlowBuffer = require('buffer').SlowBuffer;
 const vm = require('vm');
 
 [
@@ -24,7 +23,6 @@ const vm = require('vm');
 });
 
 assert(ArrayBuffer.isView(new Buffer(10)));
-assert(ArrayBuffer.isView(new SlowBuffer(10)));
 assert(ArrayBuffer.isView(Buffer.alloc(10)));
 assert(ArrayBuffer.isView(Buffer.allocUnsafe(10)));
 assert(ArrayBuffer.isView(Buffer.allocUnsafeSlow(10)));
diff --git a/test/parallel/test-buffer-failed-alloc-typed-arrays.js b/test/parallel/test-buffer-failed-alloc-typed-arrays.js
index 699475ad0a8b31..96ad77e711320d 100644
--- a/test/parallel/test-buffer-failed-alloc-typed-arrays.js
+++ b/test/parallel/test-buffer-failed-alloc-typed-arrays.js
@@ -2,7 +2,6 @@
 
 require('../common');
 const assert = require('assert');
-const SlowBuffer = require('buffer').SlowBuffer;
 
 // Test failed or zero-sized Buffer allocations not affecting typed arrays.
 // This test exists because of a regression that occurred. Because Buffer
@@ -15,7 +14,6 @@ const zeroArray = new Uint32Array(10).fill(0);
 const sizes = [1e20, 0, 0.1, -1, 'a', undefined, null, NaN];
 const allocators = [
   Buffer,
-  SlowBuffer,
   Buffer.alloc,
   Buffer.allocUnsafe,
   Buffer.allocUnsafeSlow,
diff --git a/test/parallel/test-buffer-inspect.js b/test/parallel/test-buffer-inspect.js
index 1e8212e876344a..cbefba4a8f081d 100644
--- a/test/parallel/test-buffer-inspect.js
+++ b/test/parallel/test-buffer-inspect.js
@@ -30,29 +30,20 @@ buffer.INSPECT_MAX_BYTES = 2;
 let b = Buffer.allocUnsafe(4);
 b.fill('1234');
 
-let s = buffer.SlowBuffer(4);
-s.fill('1234');
-
 let expected = '<Buffer 31 32 ... 2 more bytes>';
 
 assert.strictEqual(util.inspect(b), expected);
-assert.strictEqual(util.inspect(s), expected);
 
 b = Buffer.allocUnsafe(2);
 b.fill('12');
 
-s = buffer.SlowBuffer(2);
-s.fill('12');
-
 expected = '<Buffer 31 32>';
 
 assert.strictEqual(util.inspect(b), expected);
-assert.strictEqual(util.inspect(s), expected);
 
 buffer.INSPECT_MAX_BYTES = Infinity;
 
 assert.strictEqual(util.inspect(b), expected);
-assert.strictEqual(util.inspect(s), expected);
 
 b.inspect = undefined;
 b.prop = new Uint8Array(0);
diff --git a/test/parallel/test-buffer-no-negative-allocation.js b/test/parallel/test-buffer-no-negative-allocation.js
index 055e2d5dc69bdd..e48d9c7545755d 100644
--- a/test/parallel/test-buffer-no-negative-allocation.js
+++ b/test/parallel/test-buffer-no-negative-allocation.js
@@ -2,7 +2,6 @@
 
 require('../common');
 const assert = require('assert');
-const { SlowBuffer } = require('buffer');
 
 const msg = {
   code: 'ERR_OUT_OF_RANGE',
@@ -30,8 +29,3 @@ assert.throws(() => Buffer.allocUnsafeSlow(-Buffer.poolSize), msg);
 assert.throws(() => Buffer.allocUnsafeSlow(-100), msg);
 assert.throws(() => Buffer.allocUnsafeSlow(-1), msg);
 assert.throws(() => Buffer.allocUnsafeSlow(NaN), msg);
-
-assert.throws(() => SlowBuffer(-Buffer.poolSize), msg);
-assert.throws(() => SlowBuffer(-100), msg);
-assert.throws(() => SlowBuffer(-1), msg);
-assert.throws(() => SlowBuffer(NaN), msg);
diff --git a/test/parallel/test-buffer-over-max-length.js b/test/parallel/test-buffer-over-max-length.js
index f29d6b62d4aa40..5ee07b14d2abb5 100644
--- a/test/parallel/test-buffer-over-max-length.js
+++ b/test/parallel/test-buffer-over-max-length.js
@@ -4,7 +4,6 @@ require('../common');
 const assert = require('assert');
 
 const buffer = require('buffer');
-const SlowBuffer = buffer.SlowBuffer;
 
 const kMaxLength = buffer.kMaxLength;
 const bufferMaxSizeMsg = {
@@ -13,7 +12,6 @@ const bufferMaxSizeMsg = {
 };
 
 assert.throws(() => Buffer(kMaxLength + 1), bufferMaxSizeMsg);
-assert.throws(() => SlowBuffer(kMaxLength + 1), bufferMaxSizeMsg);
 assert.throws(() => Buffer.alloc(kMaxLength + 1), bufferMaxSizeMsg);
 assert.throws(() => Buffer.allocUnsafe(kMaxLength + 1), bufferMaxSizeMsg);
 assert.throws(() => Buffer.allocUnsafeSlow(kMaxLength + 1), bufferMaxSizeMsg);
diff --git a/test/parallel/test-buffer-slow.js b/test/parallel/test-buffer-slow.js
deleted file mode 100644
index 07138d5db0b397..00000000000000
--- a/test/parallel/test-buffer-slow.js
+++ /dev/null
@@ -1,53 +0,0 @@
-'use strict';
-
-require('../common');
-const assert = require('assert');
-const buffer = require('buffer');
-const SlowBuffer = buffer.SlowBuffer;
-
-const ones = [1, 1, 1, 1];
-
-// Should create a Buffer
-let sb = SlowBuffer(4);
-assert(sb instanceof Buffer);
-assert.strictEqual(sb.length, 4);
-sb.fill(1);
-for (const [key, value] of sb.entries()) {
-  assert.deepStrictEqual(value, ones[key]);
-}
-
-// underlying ArrayBuffer should have the same length
-assert.strictEqual(sb.buffer.byteLength, 4);
-
-// Should work without new
-sb = SlowBuffer(4);
-assert(sb instanceof Buffer);
-assert.strictEqual(sb.length, 4);
-sb.fill(1);
-for (const [key, value] of sb.entries()) {
-  assert.deepStrictEqual(value, ones[key]);
-}
-
-// Should work with edge cases
-assert.strictEqual(SlowBuffer(0).length, 0);
-
-// Should throw with invalid length type
-const bufferInvalidTypeMsg = {
-  code: 'ERR_INVALID_ARG_TYPE',
-  name: 'TypeError',
-  message: /^The "size" argument must be of type number/,
-};
-assert.throws(() => SlowBuffer(), bufferInvalidTypeMsg);
-assert.throws(() => SlowBuffer({}), bufferInvalidTypeMsg);
-assert.throws(() => SlowBuffer('6'), bufferInvalidTypeMsg);
-assert.throws(() => SlowBuffer(true), bufferInvalidTypeMsg);
-
-// Should throw with invalid length value
-const bufferMaxSizeMsg = {
-  code: 'ERR_OUT_OF_RANGE',
-  name: 'RangeError',
-};
-assert.throws(() => SlowBuffer(NaN), bufferMaxSizeMsg);
-assert.throws(() => SlowBuffer(Infinity), bufferMaxSizeMsg);
-assert.throws(() => SlowBuffer(-1), bufferMaxSizeMsg);
-assert.throws(() => SlowBuffer(buffer.kMaxLength + 1), bufferMaxSizeMsg);
diff --git a/test/parallel/test-buffer-tostring-rangeerror.js b/test/parallel/test-buffer-tostring-rangeerror.js
index 0ebea759b5c42b..ba8483c92527f5 100644
--- a/test/parallel/test-buffer-tostring-rangeerror.js
+++ b/test/parallel/test-buffer-tostring-rangeerror.js
@@ -7,7 +7,6 @@ require('../common');
 
 const assert = require('assert');
 const {
-  SlowBuffer,
   constants: {
     MAX_STRING_LENGTH,
   },
@@ -19,7 +18,6 @@ const message = {
   name: 'Error',
 };
 assert.throws(() => Buffer(len).toString('utf8'), message);
-assert.throws(() => SlowBuffer(len).toString('utf8'), message);
 assert.throws(() => Buffer.alloc(len).toString('utf8'), message);
 assert.throws(() => Buffer.allocUnsafe(len).toString('utf8'), message);
 assert.throws(() => Buffer.allocUnsafeSlow(len).toString('utf8'), message);
diff --git a/test/parallel/test-buffer-zero-fill-cli.js b/test/parallel/test-buffer-zero-fill-cli.js
index 4299f81039b0b5..79003568cf48f4 100644
--- a/test/parallel/test-buffer-zero-fill-cli.js
+++ b/test/parallel/test-buffer-zero-fill-cli.js
@@ -1,11 +1,10 @@
 'use strict';
 // Flags: --zero-fill-buffers
 
-// when using --zero-fill-buffers, every Buffer and SlowBuffer
+// when using --zero-fill-buffers, every Buffer
 // instance must be zero filled upon creation
 
 require('../common');
-const SlowBuffer = require('buffer').SlowBuffer;
 const assert = require('assert');
 
 function isZeroFilled(buf) {
@@ -22,9 +21,7 @@ for (let i = 0; i < 50; i++) {
   const bufs = [
     Buffer.alloc(20),
     Buffer.allocUnsafe(20),
-    SlowBuffer(20),
     Buffer(20),
-    new SlowBuffer(20),
   ];
   for (const buf of bufs) {
     assert(isZeroFilled(buf));
diff --git a/test/parallel/test-icu-transcode.js b/test/parallel/test-icu-transcode.js
index e9aced128eec21..20ecab7213b292 100644
--- a/test/parallel/test-icu-transcode.js
+++ b/test/parallel/test-icu-transcode.js
@@ -83,8 +83,3 @@ assert.deepStrictEqual(
   const dest = buffer.transcode(new Uint8Array(), 'utf8', 'latin1');
   assert.strictEqual(dest.length, 0);
 }
-
-// Test that it doesn't crash
-{
-  buffer.transcode(new buffer.SlowBuffer(1), 'utf16le', 'ucs2');
-}