diff --git a/static_tests/test_not_none.py b/static_tests/test_not_none.py
new file mode 100644
index 0000000..6d26854
--- /dev/null
+++ b/static_tests/test_not_none.py
@@ -0,0 +1,12 @@
+from __future__ import annotations
+
+from typing import Any
+from typing_extensions import assert_type
+
+from useful_types import not_none
+
+
+def test(x: Any, y: str | None, z: str) -> None:
+    assert_type(not_none(x), Any)
+    assert_type(not_none(y), str)
+    assert_type(not_none(z), str)
diff --git a/useful_types/__init__.py b/useful_types/__init__.py
index 064c4b9..6791c05 100644
--- a/useful_types/__init__.py
+++ b/useful_types/__init__.py
@@ -3,7 +3,7 @@
 from collections.abc import Awaitable, Iterable, Sequence, Set as AbstractSet, Sized
 from os import PathLike
 from typing import Any, TypeVar, Union, overload
-from typing_extensions import Buffer, Literal, Protocol, TypeAlias
+from typing_extensions import Buffer, Literal, Never, Protocol, TypeAlias
 
 _KT = TypeVar("_KT")
 _KT_co = TypeVar("_KT_co", covariant=True)
@@ -321,3 +321,27 @@ def __getitem__(self, __i: int) -> int:
 
 class SizedBuffer(Sized, Buffer, Protocol):
     ...
+
+
+@overload
+def not_none(obj: _T, /, message: str | None = ...) -> _T:
+    ...
+
+
+@overload
+def not_none(obj: None, /, message: str | None = ...) -> Never:
+    ...
+
+
+def not_none(obj: _T | None, /, message: str | None = None) -> _T:
+    """Raise TypeError if obj is None, otherwise return obj.
+
+    Useful for safely casting away optional types.
+
+    """
+    if obj is None:
+        if message is not None:
+            raise TypeError(message)
+        else:
+            raise TypeError("Object is unexpectedly None")
+    return obj