diff --git a/Doc/deprecations/c-api-pending-removal-in-3.17.rst b/Doc/deprecations/c-api-pending-removal-in-3.17.rst
new file mode 100644
index 00000000000000..646afbf0b078f2
--- /dev/null
+++ b/Doc/deprecations/c-api-pending-removal-in-3.17.rst
@@ -0,0 +1,4 @@
+Pending removal in Python 3.17
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* :pep:`456` embedders support for the string hashing scheme definition.
diff --git a/Doc/deprecations/index.rst b/Doc/deprecations/index.rst
index f3cecb321d633f..7579121c0633ff 100644
--- a/Doc/deprecations/index.rst
+++ b/Doc/deprecations/index.rst
@@ -18,6 +18,10 @@ C API deprecations
 
 .. include:: c-api-pending-removal-in-3.15.rst
 
+.. include:: c-api-pending-removal-in-3.16.rst
+
+.. include:: c-api-pending-removal-in-3.17.rst
+
 .. include:: c-api-pending-removal-in-3.18.rst
 
 .. include:: c-api-pending-removal-in-3.20.rst
diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
index 5379ac3abba227..8a7acef98ae6a4 100644
--- a/Doc/whatsnew/3.15.rst
+++ b/Doc/whatsnew/3.15.rst
@@ -844,6 +844,18 @@ Deprecated
 New deprecations
 ----------------
 
+* Build:
+
+  * Deprecate :pep:`456` support for providing an external definition
+    of the string hashing scheme. Removal is scheduled for Python 3.17.
+
+    Previously, embedders could define :c:macro:`Py_HASH_ALGORITHM` to be
+    ``Py_HASH_EXTERNAL`` to indicate that the hashing scheme was provided
+    externally but this feature was undocumented, untested and most likely
+    unused.
+
+    (Contributed by Bénédikt Tran in :gh:`141226`.)
+
 * CLI:
 
   * Deprecate :option:`-b` and :option:`!-bb` command-line options
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-11-09-15-44-58.gh-issue-141226.KTb_3F.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-11-09-15-44-58.gh-issue-141226.KTb_3F.rst
new file mode 100644
index 00000000000000..60bc9b201a45f3
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-11-09-15-44-58.gh-issue-141226.KTb_3F.rst
@@ -0,0 +1,3 @@
+Deprecate :pep:`456` support for providing an external definition
+of the string hashing scheme. Removal is scheduled for Python 3.17.
+Patch by Bénédikt Tran.
diff --git a/Python/pyhash.c b/Python/pyhash.c
index 216f437dd9a2d4..b6b4ee225c097e 100644
--- a/Python/pyhash.c
+++ b/Python/pyhash.c
@@ -17,7 +17,7 @@
 _Py_HashSecret_t _Py_HashSecret = {{0}};
 
 #if Py_HASH_ALGORITHM == Py_HASH_EXTERNAL
-extern PyHash_FuncDef PyHash_Func;
+Py_DEPRECATED(3.15) extern PyHash_FuncDef PyHash_Func;
 #else
 static PyHash_FuncDef PyHash_Func;
 #endif