diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index e37fde8a020..4633cff7a48 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -17,7 +17,7 @@ class ContextDecorator(object):
         return inner
 
 
-class GeneratorContextManager(ContextDecorator):
+class _GeneratorContextManager(ContextDecorator):
     """Helper for @contextmanager decorator."""
 
     def __init__(self, gen):
@@ -92,7 +92,7 @@ def contextmanager(func):
     """
     @wraps(func)
     def helper(*args, **kwds):
-        return GeneratorContextManager(func(*args, **kwds))
+        return _GeneratorContextManager(func(*args, **kwds))
     return helper
 
 
diff --git a/Lib/test/test_with.py b/Lib/test/test_with.py
index d6308e4fa47..a9d374b3244 100644
--- a/Lib/test/test_with.py
+++ b/Lib/test/test_with.py
@@ -9,26 +9,26 @@ __email__ = "mbland at acm dot org"
 import sys
 import unittest
 from collections import deque
-from contextlib import GeneratorContextManager, contextmanager
+from contextlib import _GeneratorContextManager, contextmanager
 from test.support import run_unittest
 
 
-class MockContextManager(GeneratorContextManager):
+class MockContextManager(_GeneratorContextManager):
     def __init__(self, gen):
-        GeneratorContextManager.__init__(self, gen)
+        _GeneratorContextManager.__init__(self, gen)
         self.enter_called = False
         self.exit_called = False
         self.exit_args = None
 
     def __enter__(self):
         self.enter_called = True
-        return GeneratorContextManager.__enter__(self)
+        return _GeneratorContextManager.__enter__(self)
 
     def __exit__(self, type, value, traceback):
         self.exit_called = True
         self.exit_args = (type, value, traceback)
-        return GeneratorContextManager.__exit__(self, type,
-                                                value, traceback)
+        return _GeneratorContextManager.__exit__(self, type,
+                                                 value, traceback)
 
 
 def mock_contextmanager(func):
diff --git a/Misc/NEWS b/Misc/NEWS
index 06832452f2b..0b2d346eddf 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -40,6 +40,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #10859: Make ``contextlib.GeneratorContextManager`` officially
+  private by renaming it to ``_GeneratorContextManager``.
+
 - Issue #10042: Fixed the total_ordering decorator to handle cross-type
   comparisons that could lead to infinite recursion.