diff --git a/Misc/NEWS.d/next/C_API/2026-10-21-19-55-00.gh-issue-159739.ctxt01.rst b/Misc/NEWS.d/next/C_API/2026-10-21-19-55-00.gh-issue-159739.ctxt01.rst
new file mode 100644
index 000000000000000..10c268e1043c9ed
--- /dev/null
+++ b/Misc/NEWS.d/next/C_API/2026-10-21-19-55-00.gh-issue-159739.ctxt01.rst
@@ -0,0 +1,2 @@
+Avoid a crash if a context watcher is cleared while other context watchers
+are being notified.
diff --git a/Python/context.c b/Python/context.c
index d48543c9e023a61..87f967063a27b20 100644
--- a/Python/context.c
+++ b/Python/context.c
@@ -169,8 +169,8 @@ notify_context_watchers(PyThreadState *ts, PyContextEvent event, PyObject *ctx)
         assert(i < CONTEXT_MAX_WATCHERS);
         if (bits & 1) {
             PyContext_WatchCallback cb = interp->context_watchers[i];
-            assert(cb != NULL);
-            if (cb(event, ctx) < 0) {
+            // A previous callback may have cleared this watcher.
+            if (cb != NULL && cb(event, ctx) < 0) {
                 PyErr_FormatUnraisable(
                     "Exception ignored in %s watcher callback for %R",
                     context_event_name(event), ctx);