diff --git a/21-merge-two-sorted-lists/21-merge-two-sorted-lists.py b/21-merge-two-sorted-lists/21-merge-two-sorted-lists.py
new file mode 100644
index 0000000..c1d2618
--- /dev/null
+++ b/21-merge-two-sorted-lists/21-merge-two-sorted-lists.py
@@ -0,0 +1,48 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution(object):
+    def mergeTwoLists(self, list1, list2):
+        """
+        :type list1: Optional[ListNode]
+        :type list2: Optional[ListNode]
+        :rtype: Optional[ListNode]
+        """
+        # Edge case: an empty list
+        if list1 == None:
+            return list2
+        elif list2 == None:
+            return list1
+        
+        # Inititialize merged variables
+        mergedHead = list1
+        mergedCurrent = list1
+        
+        # Pick smallest node as new head node
+        if list1.val > list2.val:
+            mergedHead = list2
+            mergedCurrent = list2
+            list2 = list2.next
+        else:
+            list1 = list1.next
+            
+        # Merge lists
+        while list1 != None and list2 != None:
+            if list1.val < list2.val:
+                mergedCurrent.next = list1
+                list1 = list1.next
+            else:
+                mergedCurrent.next = list2
+                list2 = list2.next
+            mergedCurrent = mergedCurrent.next
+            
+        # Attach the rest of the nodes
+        if list1 == None:
+            mergedCurrent.next = list2
+        elif list2 == None:
+            mergedCurrent.next = list1
+                
+        # Return merged list
+        return mergedHead
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