diff --git a/Lib/inspect.py b/Lib/inspect.py
index ff462750888c88..237f8a522469b7 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -317,6 +317,7 @@ def markcoroutinefunction(func):
     """
     if hasattr(func, '__func__'):
         func = func.__func__
+    func = functools._unwrap_partial(func)
     func._is_coroutine_marker = _is_coroutine_mark
     return func
 
diff --git a/Lib/test/test_inspect/test_inspect.py b/Lib/test/test_inspect/test_inspect.py
index dd3b7d9c5b4b5b..2085111015b644 100644
--- a/Lib/test/test_inspect/test_inspect.py
+++ b/Lib/test/test_inspect/test_inspect.py
@@ -334,6 +334,17 @@ def do_something_static():
         self.assertTrue(inspect.iscoroutinefunction(Cl3.do_something_classy))
         self.assertTrue(inspect.iscoroutinefunction(Cl3.do_something_static))
 
+        # Test markcoroutinefunction with functools.partial
+        async def _fn4():
+            pass
+
+        def fn4():
+            return _fn4()
+
+        partial_fn4 = functools.partial(fn4)
+        marked_partial_fn4 = inspect.markcoroutinefunction(partial_fn4)
+        self.assertTrue(inspect.iscoroutinefunction(marked_partial_fn4))
+
         self.assertFalse(
             inspect.iscoroutinefunction(unittest.mock.Mock()))
         self.assertTrue(
diff --git a/Misc/NEWS.d/next/Library/2025-12-10-02-31-08.gh-issue-142418.XLGNh3.rst b/Misc/NEWS.d/next/Library/2025-12-10-02-31-08.gh-issue-142418.XLGNh3.rst
new file mode 100644
index 00000000000000..28e273fe166beb
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-12-10-02-31-08.gh-issue-142418.XLGNh3.rst
@@ -0,0 +1,2 @@
+Fix markcoroutinefunction by letting it set the coroutine function marker on
+underlying function correctly.