diff --git a/Lib/test/test_pyexpat.py b/Lib/test/test_pyexpat.py
index c67bfc67479985..193d7f482e7fd4 100644
--- a/Lib/test/test_pyexpat.py
+++ b/Lib/test/test_pyexpat.py
@@ -276,6 +276,30 @@ def test_parse_again(self):
         self.assertEqual(expat.ErrorString(cm.exception.code),
                           expat.errors.XML_ERROR_FINISHED)
 
+    def test_reentrant_parse_crash(self):
+        p = expat.ParserCreate(encoding="utf-16")
+
+        def start(name, attrs):
+            def handler(data):
+                p.Parse(data, 0)
+            p.CharacterDataHandler = handler
+
+        p.StartElementHandler = start
+        data = b"\xff\xfe<\x00a\x00>\x00x\x00"
+        with self.assertRaises(RuntimeError) as cm:
+            for i in range(len(data)):
+                p.Parse(data[i:i+1], i == len(data) - 1)
+        self.assertEqual(str(cm.exception),
+                         "cannot call Parse() from within a handler")
+
+    def test_parse_normal(self):
+        p = expat.ParserCreate()
+        data = "<root><child/></root>".encode('utf-8')
+        try:
+            p.Parse(data, 1)
+        except RuntimeError:
+            self.fail("Parse() raised RuntimeError during normal operation")
+
 class NamespaceSeparatorTest(unittest.TestCase):
     def test_legal(self):
         # Tests that make sure we get errors when the namespace_separator value
diff --git a/Misc/NEWS.d/next/Library/2026-03-19-11-15-00.gh-issue-146169.manual.rst b/Misc/NEWS.d/next/Library/2026-03-19-11-15-00.gh-issue-146169.manual.rst
new file mode 100644
index 00000000000000..4ac7a6b5985aa3
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-03-19-11-15-00.gh-issue-146169.manual.rst
@@ -0,0 +1,3 @@
+Prevent re-entrant calls to ``Parse()`` from within expat handlers,
+which could cause a crash. Now raises :exc:`RuntimeError` when such a
+call is attempted.
diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index 782e552f342b17..2e4e17e148dddc 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -857,6 +857,13 @@ pyexpat_xmlparser_Parse_impl(xmlparseobject *self, PyTypeObject *cls,
                              PyObject *data, int isfinal)
 /*[clinic end generated code: output=8faffe07fe1f862a input=053e0f047e55c05a]*/
 {
+
+    if (self->in_callback) {
+        PyErr_SetString(PyExc_RuntimeError,
+            "cannot call Parse() from within a handler");
+        return NULL;
+    }
+
     const char *s;
     Py_ssize_t slen;
     Py_buffer view;