diff --git a/Lib/test/test_interpreters/test_api.py b/Lib/test/test_interpreters/test_api.py
index 5e3d7a052bae91..a9befbba64daa0 100644
--- a/Lib/test/test_interpreters/test_api.py
+++ b/Lib/test/test_interpreters/test_api.py
@@ -54,6 +54,9 @@ def test_in_main(self):
         self.assertIsInstance(interp, interpreters.Interpreter)
         self.assertIn(interp, interpreters.list_all())
 
+        # GH-126221: Passing an invalid Unicode character used to cause a SystemError
+        self.assertRaises(UnicodeEncodeError, _interpreters.create, '\udc80')
+
     def test_in_thread(self):
         lock = threading.Lock()
         interp = None
diff --git a/Misc/NEWS.d/next/Library/2024-10-30-23-42-44.gh-issue-126223.k2qooc.rst b/Misc/NEWS.d/next/Library/2024-10-30-23-42-44.gh-issue-126223.k2qooc.rst
new file mode 100644
index 00000000000000..fee391c030b941
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-10-30-23-42-44.gh-issue-126223.k2qooc.rst
@@ -0,0 +1,2 @@
+Raise a :exc:`UnicodeEncodeError` instead of a :exc:`SystemError` upon
+calling :func:`!_interpreters.create` with an invalid Unicode character.
diff --git a/Modules/_interpretersmodule.c b/Modules/_interpretersmodule.c
index 6f3392fe6ea28d..63f2bb38768511 100644
--- a/Modules/_interpretersmodule.c
+++ b/Modules/_interpretersmodule.c
@@ -402,7 +402,11 @@ config_from_object(PyObject *configobj, PyInterpreterConfig *config)
         }
     }
     else if (PyUnicode_Check(configobj)) {
-        if (init_named_config(config, PyUnicode_AsUTF8(configobj)) < 0) {
+        const char *utf8name = PyUnicode_AsUTF8(configobj);
+        if (utf8name == NULL) {
+            return -1;
+        }
+        if (init_named_config(config, utf8name) < 0) {
             return -1;
         }
     }