diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -36,6 +36,7 @@ import _testcapi
 from collections import deque, UserList
 from itertools import cycle, count
 from test import support
+from test.script_helper import assert_python_ok
 
 import codecs
 import io  # C implementation of io
@@ -2589,8 +2590,37 @@ class TextIOWrapperTest(unittest.TestCas
                                encoding='quopri_codec')
         self.assertRaises(TypeError, t.read)
 
+    def _check_create_at_shutdown(self, **kwargs):
+        # Issue #20037: creating a TextIOWrapper at shutdown
+        # shouldn't crash the interpreter.
+        iomod = self.io.__name__
+        code = """if 1:
+            import {iomod} as io
+            class C:
+                def __init__(self):
+                    self.buf = io.BytesIO()
+                def __del__(self):
+                    io.TextIOWrapper(self.buf, **{kwargs})
+            c = C()
+            """.format(iomod=iomod, kwargs=kwargs)
+        return assert_python_ok("-c", code)
+
+    def test_create_at_shutdown_without_encoding(self):
+        rc, out, err = self._check_create_at_shutdown()
+        if err:
+            # Can error out with a RuntimeError if the module state
+            # isn't found.
+            self.assertIn("RuntimeError: could not find io module state",
+                          err.decode())
+
+    def test_create_at_shutdown_with_encoding(self):
+        rc, out, err = self._check_create_at_shutdown(encoding='utf-8',
+                                                      errors='strict')
+        self.assertFalse(err)
+
 
 class CTextIOWrapperTest(TextIOWrapperTest):
+    io = io
 
     def test_initialization(self):
         r = self.BytesIO(b"\xc3\xa9\n\n")
@@ -2634,7 +2664,7 @@ class CTextIOWrapperTest(TextIOWrapperTe
 
 
 class PyTextIOWrapperTest(TextIOWrapperTest):
-    pass
+    io = pyio
 
 
 class IncrementalNewlineDecoderTest(unittest.TestCase):
diff --git a/Modules/_io/_iomodule.c b/Modules/_io/_iomodule.c
--- a/Modules/_io/_iomodule.c
+++ b/Modules/_io/_iomodule.c
@@ -539,6 +539,20 @@ int
 }
 
 
+_PyIO_State *
+_PyIO_get_module_state(void)
+{
+    PyObject *mod = PyState_FindModule(&_PyIO_Module);
+    _PyIO_State *state;
+    if (mod == NULL || (state = IO_MOD_STATE(mod)) == NULL) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "could not find io module state "
+                        "(interpreter shutdown?)");
+        return NULL;
+    }
+    return state;
+}
+
 PyObject *
 _PyIO_get_locale_module(_PyIO_State *state)
 {
diff --git a/Modules/_io/_iomodule.h b/Modules/_io/_iomodule.h
--- a/Modules/_io/_iomodule.h
+++ b/Modules/_io/_iomodule.h
@@ -135,8 +135,9 @@ typedef struct {
 } _PyIO_State;
 
 #define IO_MOD_STATE(mod) ((_PyIO_State *)PyModule_GetState(mod))
-#define IO_STATE IO_MOD_STATE(PyState_FindModule(&_PyIO_Module))
+#define IO_STATE _PyIO_get_module_state()
 
+extern _PyIO_State *_PyIO_get_module_state(void);
 extern PyObject *_PyIO_get_locale_module(_PyIO_State *);
 
 extern PyObject *_PyIO_str_close;
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -91,7 +91,9 @@ bufferediobase_readinto(PyObject *self, 
 static PyObject *
 bufferediobase_unsupported(const char *message)
 {
-    PyErr_SetString(IO_STATE->unsupported_operation, message);
+    _PyIO_State *state = IO_STATE;
+    if (state != NULL)
+        PyErr_SetString(state->unsupported_operation, message);
     return NULL;
 }
 
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -493,8 +493,10 @@ err_closed(void)
 static PyObject *
 err_mode(char *action)
 {
-    PyErr_Format(IO_STATE->unsupported_operation,
-                 "File not open for %s", action);
+    _PyIO_State *state = IO_STATE;
+    if (state != NULL)
+        PyErr_Format(state->unsupported_operation,
+                     "File not open for %s", action);
     return NULL;
 }
 
diff --git a/Modules/_io/iobase.c b/Modules/_io/iobase.c
--- a/Modules/_io/iobase.c
+++ b/Modules/_io/iobase.c
@@ -69,7 +69,9 @@ PyDoc_STRVAR(iobase_doc,
 static PyObject *
 iobase_unsupported(const char *message)
 {
-    PyErr_SetString(IO_STATE->unsupported_operation, message);
+    _PyIO_State *state = IO_STATE;
+    if (state != NULL)
+        PyErr_SetString(state->unsupported_operation, message);
     return NULL;
 }
 
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -45,7 +45,9 @@ PyDoc_STRVAR(textiobase_doc,
 static PyObject *
 _unsupported(const char *message)
 {
-    PyErr_SetString(IO_STATE->unsupported_operation, message);
+    _PyIO_State *state = IO_STATE;
+    if (state != NULL)
+        PyErr_SetString(state->unsupported_operation, message);
     return NULL;
 }
 
@@ -852,7 +854,7 @@ textiowrapper_init(textio *self, PyObjec
     char *errors = NULL;
     char *newline = NULL;
     int line_buffering = 0, write_through = 0;
-    _PyIO_State *state = IO_STATE;
+    _PyIO_State *state = NULL;
 
     PyObject *res;
     int r;
@@ -891,6 +893,9 @@ textiowrapper_init(textio *self, PyObjec
     if (encoding == NULL) {
         /* Try os.device_encoding(fileno) */
         PyObject *fileno;
+        state = IO_STATE;
+        if (state == NULL)
+            goto error;
         fileno = _PyObject_CallMethodId(buffer, &PyId_fileno, NULL);
         /* Ignore only AttributeError and UnsupportedOperation */
         if (fileno == NULL) {