diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-29-15-10-59.gh-issue-149162.BPPyrq.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-29-15-10-59.gh-issue-149162.BPPyrq.rst
new file mode 100644
index 00000000000000..b4c443ecee07ad
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-29-15-10-59.gh-issue-149162.BPPyrq.rst
@@ -0,0 +1,3 @@
+Fix a potential deadlock in :c:func:`PyUnicode_InternFromString` and other
+interning functions in the :term:`free-threaded build` when called from C++
+static local initializers.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index e249473cd79e3b..6bd9e7d607cc41 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -113,7 +113,9 @@ NOTE: In the interpreter's initialization phase, some globals are currently
 #endif
 
 #ifdef Py_GIL_DISABLED
-#  define LOCK_INTERNED(interp) PyMutex_Lock(&_Py_INTERP_CACHED_OBJECT(interp, interned_mutex))
+#  define LOCK_INTERNED(interp) \
+    PyMutex_LockFlags(&_Py_INTERP_CACHED_OBJECT(interp, interned_mutex), \
+                      _Py_LOCK_DONT_DETACH)
 #  define UNLOCK_INTERNED(interp) PyMutex_Unlock(&_Py_INTERP_CACHED_OBJECT(interp, interned_mutex))
 #else
 #  define LOCK_INTERNED(interp)