diff --git a/merge-two-sorted-lists/gitsunmin.ts b/merge-two-sorted-lists/gitsunmin.ts
new file mode 100644
index 00000000..23bc3d6d
--- /dev/null
+++ b/merge-two-sorted-lists/gitsunmin.ts
@@ -0,0 +1,44 @@
+/**
+ * https://leetcode.com/problems/merge-two-sorted-lists
+ * time complexity : O(n)
+ * space complexity : O(1)
+ */
+
+class ListNode {
+    val: number
+    next: ListNode | null
+    constructor(val?: number, next?: ListNode | null) {
+        this.val = (val === undefined ? 0 : val)
+        this.next = (next === undefined ? null : next)
+    }
+}
+
+function mergeTwoLists(list1: ListNode | null, list2: ListNode | null): ListNode | null {
+    if (!list1 && !list2) return null;
+    if (!list1) return list2;
+    if (!list2) return list1;
+
+    const dummy = new ListNode();
+    let current = dummy;
+
+    while (list1 && list2) {
+        if (list1.val < list2.val) {
+            current.next = list1;
+            list1 = list1.next;
+        } else {
+            current.next = list2;
+            list2 = list2.next;
+        }
+        current = current.next;
+    }
+
+    current.next = list1 || list2;
+
+    return dummy.next;
+};
+
+const input1 = new ListNode(1, new ListNode(2, new ListNode(4)));
+const input2 = new ListNode(1, new ListNode(3, new ListNode(4)));
+
+console.log('output1:', mergeTwoLists(input1, input2));
+console.log('output2:', mergeTwoLists(input2, input1));