diff --git a/sphinx/util/inspect.py b/sphinx/util/inspect.py
index 15f0d66e2..d51d6854c 100644
--- a/sphinx/util/inspect.py
+++ b/sphinx/util/inspect.py
@@ -13,6 +13,7 @@ import enum
 import inspect
 import re
 import sys
+import types
 import typing
 import warnings
 from functools import partial, partialmethod
@@ -304,6 +305,18 @@ def isproperty(obj: Any) -> bool:
     return isinstance(obj, property)
 
 
+def isgenericalias(obj: Any) -> bool:
+    """Check if the object is GenericAlias."""
+    if (hasattr(typing, '_GenericAlias') and  # only for py37+
+            isinstance(obj, typing._GenericAlias)):  # type: ignore
+        return True
+    elif (hasattr(types, 'GenericAlias') and  # only for py39+
+          isinstance(obj, types.GenericAlias)):  # type: ignore
+        return True
+    else:
+        return False
+
+
 def safe_getattr(obj: Any, name: str, *defargs: Any) -> Any:
     """A getattr() that turns all exceptions into AttributeErrors."""
     try:
diff --git a/tests/roots/test-ext-autodoc/target/genericalias.py b/tests/roots/test-ext-autodoc/target/genericalias.py
new file mode 100644
index 000000000..78b68cd63
--- /dev/null
+++ b/tests/roots/test-ext-autodoc/target/genericalias.py
@@ -0,0 +1,6 @@
+from typing import List, Callable
+
+#: A list of int
+T = List[int]
+
+C = Callable[[int], None]  # a generic alias not having a doccomment
diff --git a/tests/test_util_inspect.py b/tests/test_util_inspect.py
index f16feb698..ae4c34962 100644
--- a/tests/test_util_inspect.py
+++ b/tests/test_util_inspect.py
@@ -560,6 +560,18 @@ def test_isproperty(app):
     assert inspect.isproperty(func) is False            # function
 
 
+@pytest.mark.skipif(sys.version_info < (3, 7), reason='python 3.7+ is required.')
+@pytest.mark.sphinx(testroot='ext-autodoc')
+def test_isgenericalias(app):
+    from target.genericalias import C, T
+    from target.methods import Base
+
+    assert inspect.isgenericalias(C) is True
+    assert inspect.isgenericalias(T) is True
+    assert inspect.isgenericalias(object()) is False
+    assert inspect.isgenericalias(Base) is False
+
+
 def test_unpartial():
     def func1(a, b, c):
         pass