diff --git a/Lib/test/test_free_threading/test_bisect.py b/Lib/test/test_free_threading/test_bisect.py
new file mode 100644
index 00000000000000..de6ea89d885f9b
--- /dev/null
+++ b/Lib/test/test_free_threading/test_bisect.py
@@ -0,0 +1,43 @@
+import unittest
+
+from itertools import cycle
+
+from test.support import import_helper, threading_helper, subTests
+from test.support.threading_helper import run_concurrently
+
+bisect = import_helper.import_module("bisect")
+
+
+NTHREADS = 10
+
+
+@threading_helper.requires_working_threading()
+class TestBisect(unittest.TestCase):
+    @subTests("insort_func", [bisect.insort_left, bisect.insort_right])
+    def test_racing_insort(self, insort_func):
+        lst = list(range(10))
+        insort_items_iter = cycle(list(range(11)))
+
+        def worker(lst, insort_items_iter):
+            for _ in range(10):
+                insort_item = next(insort_items_iter)
+                insort_func(lst, insort_item)
+
+        run_concurrently(
+            worker_func=worker,
+            nthreads=NTHREADS,
+            args=(lst, insort_items_iter),
+        )
+
+        self.assertTrue(self.is_sorted_ascending(lst))
+
+    @staticmethod
+    def is_sorted_ascending(lst):
+        """
+        Check if the list is sorted in ascending order (non-decreasing).
+        """
+        return all(lst[i - 1] <= lst[i] for i in range(1, len(lst)))
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-07-22-11-09-16.gh-issue-116738.uAgWNZ.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-07-22-11-09-16.gh-issue-116738.uAgWNZ.rst
new file mode 100644
index 00000000000000..654545cf9da202
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-07-22-11-09-16.gh-issue-116738.uAgWNZ.rst
@@ -0,0 +1,2 @@
+Make functions in :mod:`bisect` thread-safe on the :term:`free threaded
+<free threading>` build.
diff --git a/Modules/_bisectmodule.c b/Modules/_bisectmodule.c
index 9b146265445d9a..90192c2508e8c5 100644
--- a/Modules/_bisectmodule.c
+++ b/Modules/_bisectmodule.c
@@ -179,6 +179,7 @@ _bisect_bisect_right_impl(PyObject *module, PyObject *a, PyObject *x,
 }
 
 /*[clinic input]
+@critical_section a
 _bisect.insort_right
 
     a: object
@@ -201,7 +202,7 @@ A custom key function can be supplied to customize the sort order.
 static PyObject *
 _bisect_insort_right_impl(PyObject *module, PyObject *a, PyObject *x,
                           Py_ssize_t lo, Py_ssize_t hi, PyObject *key)
-/*[clinic end generated code: output=ac3bf26d07aedda2 input=f60777d2b6ddb239]*/
+/*[clinic end generated code: output=ac3bf26d07aedda2 input=93bd855be0c1add7]*/
 {
     PyObject *result, *key_x;
     Py_ssize_t index;
@@ -365,6 +366,7 @@ _bisect_bisect_left_impl(PyObject *module, PyObject *a, PyObject *x,
 
 
 /*[clinic input]
+@critical_section a
 _bisect.insort_left
 
     a: object
@@ -387,7 +389,7 @@ A custom key function can be supplied to customize the sort order.
 static PyObject *
 _bisect_insort_left_impl(PyObject *module, PyObject *a, PyObject *x,
                          Py_ssize_t lo, Py_ssize_t hi, PyObject *key)
-/*[clinic end generated code: output=b1d33e5e7ffff11e input=0a700a82edbd472c]*/
+/*[clinic end generated code: output=b1d33e5e7ffff11e input=93e06f5a323e09ef]*/
 {
     PyObject *result, *key_x;
     Py_ssize_t index;
diff --git a/Modules/clinic/_bisectmodule.c.h b/Modules/clinic/_bisectmodule.c.h
index 314208bc41d0c1..bc9d7d020d9423 100644
--- a/Modules/clinic/_bisectmodule.c.h
+++ b/Modules/clinic/_bisectmodule.c.h
@@ -7,6 +7,7 @@ preserve
 #  include "pycore_runtime.h"     // _Py_ID()
 #endif
 #include "pycore_abstract.h"      // _PyNumber_Index()
+#include "pycore_critical_section.h"// Py_BEGIN_CRITICAL_SECTION()
 #include "pycore_modsupport.h"    // _PyArg_UnpackKeywords()
 
 PyDoc_STRVAR(_bisect_bisect_right__doc__,
@@ -222,7 +223,9 @@ _bisect_insort_right(PyObject *module, PyObject *const *args, Py_ssize_t nargs,
     }
     key = args[4];
 skip_optional_kwonly:
+    Py_BEGIN_CRITICAL_SECTION(a);
     return_value = _bisect_insort_right_impl(module, a, x, lo, hi, key);
+    Py_END_CRITICAL_SECTION();
 
 exit:
     return return_value;
@@ -441,9 +444,11 @@ _bisect_insort_left(PyObject *module, PyObject *const *args, Py_ssize_t nargs, P
     }
     key = args[4];
 skip_optional_kwonly:
+    Py_BEGIN_CRITICAL_SECTION(a);
     return_value = _bisect_insort_left_impl(module, a, x, lo, hi, key);
+    Py_END_CRITICAL_SECTION();
 
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=729385c6a23828ab input=a9049054013a1b77]*/
+/*[clinic end generated code: output=6111121f07c8300b input=a9049054013a1b77]*/