diff --git a/Include/pystate.h b/Include/pystate.h
index bbeea9d51b8..e410665e35d 100644
--- a/Include/pystate.h
+++ b/Include/pystate.h
@@ -245,6 +245,13 @@ typedef struct _ts {
 PyAPI_FUNC(PyInterpreterState *) PyInterpreterState_New(void);
 PyAPI_FUNC(void) PyInterpreterState_Clear(PyInterpreterState *);
 PyAPI_FUNC(void) PyInterpreterState_Delete(PyInterpreterState *);
+#if !defined(Py_LIMITED_API)
+PyAPI_FUNC(PyInterpreterState *) _PyInterpreterState_Get(void);
+#endif
+#ifdef Py_BUILD_CORE
+   /* Macro which should only be used for performance critical code */
+#  define _PyInterpreterState_GET_UNSAFE() (PyThreadState_GET()->interp)
+#endif
 #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03070000
 /* New in 3.7 */
 PyAPI_FUNC(int64_t) PyInterpreterState_GetID(PyInterpreterState *);
diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 69e27be9cc8..f6b39defbc8 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -1049,7 +1049,7 @@ thread_PyThread_start_new_thread(PyObject *self, PyObject *fargs)
     boot = PyMem_NEW(struct bootstate, 1);
     if (boot == NULL)
         return PyErr_NoMemory();
-    boot->interp = PyThreadState_GET()->interp;
+    boot->interp = _PyInterpreterState_Get();
     boot->func = func;
     boot->args = args;
     boot->keyw = keyw;
@@ -1154,8 +1154,8 @@ A thread's identity may be reused for another thread after it exits.");
 static PyObject *
 thread__count(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
-    PyThreadState *tstate = PyThreadState_Get();
-    return PyLong_FromLong(tstate->interp->num_threads);
+    PyInterpreterState *interp = _PyInterpreterState_Get();
+    return PyLong_FromLong(interp->num_threads);
 }
 
 PyDoc_STRVAR(_count_doc,
@@ -1348,7 +1348,7 @@ PyInit__thread(void)
     PyObject *m, *d, *v;
     double time_max;
     double timeout_max;
-    PyThreadState *tstate = PyThreadState_Get();
+    PyInterpreterState *interp = _PyInterpreterState_Get();
 
     /* Initialize types: */
     if (PyType_Ready(&localdummytype) < 0)
@@ -1395,7 +1395,7 @@ PyInit__thread(void)
     if (PyModule_AddObject(m, "_local", (PyObject *)&localtype) < 0)
         return NULL;
 
-    tstate->interp->num_threads = 0;
+    interp->num_threads = 0;
 
     str_dict = PyUnicode_InternFromString("__dict__");
     if (str_dict == NULL)
diff --git a/Modules/_xxsubinterpretersmodule.c b/Modules/_xxsubinterpretersmodule.c
index 8567e4fd970..6162c53b9e6 100644
--- a/Modules/_xxsubinterpretersmodule.c
+++ b/Modules/_xxsubinterpretersmodule.c
@@ -26,10 +26,9 @@ _copy_raw_string(PyObject *strobj)
 static PyInterpreterState *
 _get_current(void)
 {
-    PyThreadState *tstate = PyThreadState_Get();
-    // PyThreadState_Get() aborts if lookup fails, so we don't need
+    // _PyInterpreterState_Get() aborts if lookup fails, so don't need
     // to check the result for NULL.
-    return tstate->interp;
+    return _PyInterpreterState_Get();
 }
 
 static int64_t
@@ -1941,7 +1940,7 @@ _run_script_in_interpreter(PyInterpreterState *interp, const char *codestr,
 
     // Switch to interpreter.
     PyThreadState *save_tstate = NULL;
-    if (interp != PyThreadState_Get()->interp) {
+    if (interp != _PyInterpreterState_Get()) {
         // XXX Using the "head" thread isn't strictly correct.
         PyThreadState *tstate = PyInterpreterState_ThreadHead(interp);
         // XXX Possible GILState issues?
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 6104c0f74de..3e03039f15b 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -437,7 +437,7 @@ run_at_forkers(PyObject *lst, int reverse)
 void
 PyOS_BeforeFork(void)
 {
-    run_at_forkers(PyThreadState_Get()->interp->before_forkers, 1);
+    run_at_forkers(_PyInterpreterState_Get()->before_forkers, 1);
 
     _PyImport_AcquireLock();
 }
@@ -448,7 +448,7 @@ PyOS_AfterFork_Parent(void)
     if (_PyImport_ReleaseLock() <= 0)
         Py_FatalError("failed releasing import lock after fork");
 
-    run_at_forkers(PyThreadState_Get()->interp->after_forkers_parent, 0);
+    run_at_forkers(_PyInterpreterState_Get()->after_forkers_parent, 0);
 }
 
 void
@@ -459,7 +459,7 @@ PyOS_AfterFork_Child(void)
     _PyImport_ReInitLock();
     _PySignal_AfterFork();
 
-    run_at_forkers(PyThreadState_Get()->interp->after_forkers_child, 0);
+    run_at_forkers(_PyInterpreterState_Get()->after_forkers_child, 0);
 }
 
 static int
@@ -5655,7 +5655,7 @@ os_register_at_fork_impl(PyObject *module, PyObject *before,
         check_null_or_callable(after_in_parent, "after_in_parent")) {
         return NULL;
     }
-    interp = PyThreadState_Get()->interp;
+    interp = _PyInterpreterState_Get();
 
     if (register_at_forker(&interp->before_forkers, before)) {
         return NULL;
diff --git a/Modules/zipimport.c b/Modules/zipimport.c
index 57e7a13137f..4df4ba9f8b8 100644
--- a/Modules/zipimport.c
+++ b/Modules/zipimport.c
@@ -1074,7 +1074,7 @@ read_directory(PyObject *archive)
         if (flags & 0x0800) {
             charset = "utf-8";
         }
-        else if (!PyThreadState_GET()->interp->codecs_initialized) {
+        else if (!_PyInterpreterState_Get()->codecs_initialized) {
             /* During bootstrap, we may need to load the encodings
                package from a ZIP file. But the cp437 encoding is implemented
                in Python in the encodings package.
@@ -1351,7 +1351,7 @@ unmarshal_code(PyObject *pathname, PyObject *data, time_t mtime)
 
     uint32_t flags = get_uint32(buf + 4);
     if (flags != 0) {
-        _PyCoreConfig *config = &PyThreadState_GET()->interp->core_config;
+        _PyCoreConfig *config = &_PyInterpreterState_Get()->core_config;
         // Hash-based pyc. We currently refuse to handle checked hash-based
         // pycs. We could validate hash-based pycs against the source, but it
         // seems likely that most people putting hash-based pycs in a zipfile
diff --git a/Objects/codeobject.c b/Objects/codeobject.c
index b07667c28df..cedf11ee8af 100644
--- a/Objects/codeobject.c
+++ b/Objects/codeobject.c
@@ -3,6 +3,7 @@
 #include "Python.h"
 #include "code.h"
 #include "structmember.h"
+#include "internal/pystate.h"
 
 /* Holder for co_extra information */
 typedef struct {
@@ -428,7 +429,7 @@ static void
 code_dealloc(PyCodeObject *co)
 {
     if (co->co_extra != NULL) {
-        PyInterpreterState *interp = PyThreadState_Get()->interp;
+        PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
         _PyCodeObjectExtra *co_extra = co->co_extra;
 
         for (Py_ssize_t i = 0; i < co_extra->ce_size; i++) {
@@ -871,7 +872,7 @@ _PyCode_GetExtra(PyObject *code, Py_ssize_t index, void **extra)
 int
 _PyCode_SetExtra(PyObject *code, Py_ssize_t index, void *extra)
 {
-    PyInterpreterState *interp = PyThreadState_Get()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
 
     if (!PyCode_Check(code) || index < 0 ||
             index >= interp->co_extra_user_count) {
diff --git a/Objects/listobject.c b/Objects/listobject.c
index 4108f502023..308ae83fa6f 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -85,7 +85,7 @@ static size_t count_reuse = 0;
 static void
 show_alloc(void)
 {
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     if (!interp->core_config.show_alloc_count) {
         return;
     }
diff --git a/Objects/moduleobject.c b/Objects/moduleobject.c
index 5fad4474be0..2156ca0765a 100644
--- a/Objects/moduleobject.c
+++ b/Objects/moduleobject.c
@@ -173,7 +173,7 @@ _add_methods_to_object(PyObject *module, PyObject *name, PyMethodDef *functions)
 PyObject *
 PyModule_Create2(struct PyModuleDef* module, int module_api_version)
 {
-    if (!_PyImport_IsInitialized(PyThreadState_GET()->interp))
+    if (!_PyImport_IsInitialized(_PyInterpreterState_Get()))
         Py_FatalError("Python import machinery not initialized");
     return _PyModule_CreateInitialized(module, module_api_version);
 }
@@ -693,8 +693,7 @@ module_dealloc(PyModuleObject *m)
 static PyObject *
 module_repr(PyModuleObject *m)
 {
-    PyThreadState *tstate = PyThreadState_GET();
-    PyInterpreterState *interp = tstate->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
 
     return PyObject_CallMethod(interp->importlib, "_module_repr", "O", m);
 }
diff --git a/Objects/object.c b/Objects/object.c
index 2471f6b0588..6498756c92b 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -96,7 +96,7 @@ extern Py_ssize_t null_strings, one_strings;
 void
 dump_counts(FILE* f)
 {
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     if (!interp->core_config.show_alloc_count) {
         return;
     }
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index e268f75be71..eaf92d57f3f 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -44,7 +44,7 @@ static Py_ssize_t count_tracked = 0;
 static void
 show_track(void)
 {
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     if (!interp->core_config.show_alloc_count) {
         return;
     }
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 2b06f15f6c6..04fd6d03b46 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -3413,7 +3413,7 @@ PyUnicode_EncodeFSDefault(PyObject *unicode)
 #if defined(__APPLE__)
     return _PyUnicode_AsUTF8String(unicode, Py_FileSystemDefaultEncodeErrors);
 #else
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     /* Bootstrap check: if the filesystem codec is implemented in Python, we
        cannot use it to encode and decode filenames before it is loaded. Load
        the Python codec requires to encode at least its own filename. Use the C
@@ -3639,7 +3639,7 @@ PyUnicode_DecodeFSDefaultAndSize(const char *s, Py_ssize_t size)
 #if defined(__APPLE__)
     return PyUnicode_DecodeUTF8Stateful(s, size, Py_FileSystemDefaultEncodeErrors, NULL);
 #else
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     /* Bootstrap check: if the filesystem codec is implemented in Python, we
        cannot use it to encode and decode filenames before it is loaded. Load
        the Python codec requires to encode at least its own filename. Use the C
diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index 3ed42d67f83..027de484545 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -306,7 +306,7 @@ dump_config(void)
         exit(1); \
     }
 
-    PyInterpreterState *interp = PyThreadState_Get()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     _PyCoreConfig *config = &interp->core_config;
 
     printf("install_signal_handlers = %i\n", config->install_signal_handlers);
diff --git a/Python/_warnings.c b/Python/_warnings.c
index d6614b2cf6d..2229206b25c 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -78,7 +78,7 @@ get_warnings_attr(_Py_Identifier *attr_id, int try_import)
            gone, then we can't even use PyImport_GetModule without triggering
            an interpreter abort.
         */
-        if (!PyThreadState_GET()->interp->modules) {
+        if (!_PyInterpreterState_GET_UNSAFE()->modules) {
             return NULL;
         }
         warnings_module = PyImport_GetModule(warnings_str);
@@ -686,7 +686,7 @@ setup_context(Py_ssize_t stack_level, PyObject **filename, int *lineno,
     }
 
     if (f == NULL) {
-        globals = PyThreadState_Get()->interp->sysdict;
+        globals = _PyInterpreterState_GET_UNSAFE()->sysdict;
         *filename = PyUnicode_FromString("sys");
         *lineno = 1;
     }
diff --git a/Python/ceval.c b/Python/ceval.c
index 46da295aac0..f3a74b00a2b 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -532,8 +532,8 @@ PyEval_EvalFrame(PyFrameObject *f) {
 PyObject *
 PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
 {
-    PyThreadState *tstate = PyThreadState_GET();
-    return tstate->interp->eval_frame(f, throwflag);
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
+    return interp->eval_frame(f, throwflag);
 }
 
 PyObject* _Py_HOT_FUNCTION
@@ -4435,7 +4435,7 @@ PyEval_GetBuiltins(void)
 {
     PyFrameObject *current_frame = PyEval_GetFrame();
     if (current_frame == NULL)
-        return PyThreadState_GET()->interp->builtins;
+        return _PyInterpreterState_GET_UNSAFE()->builtins;
     else
         return current_frame->f_builtins;
 }
@@ -4769,7 +4769,7 @@ import_name(PyFrameObject *f, PyObject *name, PyObject *fromlist, PyObject *leve
     }
 
     /* Fast path for not overloaded __import__. */
-    if (import_func == PyThreadState_GET()->interp->import_func) {
+    if (import_func == _PyInterpreterState_GET_UNSAFE()->import_func) {
         int ilevel = _PyLong_AsInt(level);
         if (ilevel == -1 && PyErr_Occurred()) {
             return NULL;
@@ -5136,7 +5136,7 @@ _Py_GetDXProfile(PyObject *self, PyObject *args)
 Py_ssize_t
 _PyEval_RequestCodeExtraIndex(freefunc free)
 {
-    PyInterpreterState *interp = PyThreadState_Get()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     Py_ssize_t new_index;
 
     if (interp->co_extra_user_count == MAX_CO_EXTRA_USERS - 1) {
diff --git a/Python/codecs.c b/Python/codecs.c
index eb3cd35fb8e..4062429fe35 100644
--- a/Python/codecs.c
+++ b/Python/codecs.c
@@ -32,7 +32,7 @@ static int _PyCodecRegistry_Init(void); /* Forward */
 
 int PyCodec_Register(PyObject *search_function)
 {
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     if (interp->codec_search_path == NULL && _PyCodecRegistry_Init())
         goto onError;
     if (search_function == NULL) {
@@ -99,7 +99,6 @@ PyObject *normalizestring(const char *string)
 
 PyObject *_PyCodec_Lookup(const char *encoding)
 {
-    PyInterpreterState *interp;
     PyObject *result, *args = NULL, *v;
     Py_ssize_t i, len;
 
@@ -108,7 +107,7 @@ PyObject *_PyCodec_Lookup(const char *encoding)
         goto onError;
     }
 
-    interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     if (interp->codec_search_path == NULL && _PyCodecRegistry_Init())
         goto onError;
 
@@ -187,11 +186,10 @@ PyObject *_PyCodec_Lookup(const char *encoding)
 
 int _PyCodec_Forget(const char *encoding)
 {
-    PyInterpreterState *interp;
     PyObject *v;
     int result;
 
-    interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     if (interp->codec_search_path == NULL) {
         return -1;
     }
@@ -624,7 +622,7 @@ PyObject *_PyCodec_DecodeText(PyObject *object,
    Return 0 on success, -1 on error */
 int PyCodec_RegisterError(const char *name, PyObject *error)
 {
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     if (interp->codec_search_path == NULL && _PyCodecRegistry_Init())
         return -1;
     if (!PyCallable_Check(error)) {
@@ -642,7 +640,7 @@ PyObject *PyCodec_LookupError(const char *name)
 {
     PyObject *handler = NULL;
 
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     if (interp->codec_search_path == NULL && _PyCodecRegistry_Init())
         return NULL;
 
@@ -1494,7 +1492,7 @@ static int _PyCodecRegistry_Init(void)
         }
     };
 
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     PyObject *mod;
     unsigned i;
 
diff --git a/Python/dynload_shlib.c b/Python/dynload_shlib.c
index f2711931908..73ae26d1314 100644
--- a/Python/dynload_shlib.c
+++ b/Python/dynload_shlib.c
@@ -91,7 +91,7 @@ _PyImport_FindSharedFuncptr(const char *prefix,
         }
     }
 
-    dlopenflags = PyThreadState_GET()->interp->dlopenflags;
+    dlopenflags = _PyInterpreterState_Get()->dlopenflags;
 
     handle = dlopen(pathname, dlopenflags);
 
diff --git a/Python/import.c b/Python/import.c
index 71d5ea192db..319b661f1f9 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -304,7 +304,7 @@ _PyImport_Fini2(void)
 PyObject *
 PyImport_GetModuleDict(void)
 {
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     if (interp->modules == NULL) {
         Py_FatalError("PyImport_GetModuleDict: no module dictionary!");
     }
@@ -397,7 +397,7 @@ PyImport_Cleanup(void)
 {
     Py_ssize_t pos;
     PyObject *key, *value, *dict;
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     PyObject *modules = PyImport_GetModuleDict();
     PyObject *weaklist = NULL;
     const char * const *p;
@@ -592,7 +592,7 @@ long
 PyImport_GetMagicNumber(void)
 {
     long res;
-    PyInterpreterState *interp = PyThreadState_Get()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     PyObject *external, *pyc_magic;
 
     external = PyObject_GetAttrString(interp->importlib, "_bootstrap_external");
@@ -892,7 +892,7 @@ PyImport_ExecCodeModuleWithPathnames(const char *name, PyObject *co,
             goto error;
     }
     else if (cpathobj != NULL) {
-        PyInterpreterState *interp = PyThreadState_GET()->interp;
+        PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
         _Py_IDENTIFIER(_get_sourcefile);
 
         if (interp == NULL) {
@@ -972,7 +972,7 @@ PyImport_ExecCodeModuleObject(PyObject *name, PyObject *co, PyObject *pathname,
                               PyObject *cpathname)
 {
     PyObject *d, *external, *res;
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     _Py_IDENTIFIER(_fix_up_module);
 
     d = module_dict_for_exec(name);
@@ -1619,7 +1619,7 @@ import_find_and_load(PyObject *abs_name)
 {
     _Py_IDENTIFIER(_find_and_load);
     PyObject *mod = NULL;
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     int import_time = interp->core_config.import_time;
     static int import_level;
     static _PyTime_t accumulated;
@@ -1680,7 +1680,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
     PyObject *final_mod = NULL;
     PyObject *mod = NULL;
     PyObject *package = NULL;
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     int has_from;
 
     if (name == NULL) {
@@ -2289,7 +2289,7 @@ PyInit__imp(void)
     d = PyModule_GetDict(m);
     if (d == NULL)
         goto failure;
-    _PyCoreConfig *config = &PyThreadState_GET()->interp->core_config;
+    _PyCoreConfig *config = &_PyInterpreterState_Get()->core_config;
     PyObject *pyc_mode = PyUnicode_FromString(config->_check_hash_pycs_mode);
     if (pyc_mode == NULL) {
         goto failure;
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 95fb8616b52..c2ee4ffc468 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -2123,11 +2123,7 @@ _Py_FatalInitError(_PyInitError err)
 /* For the atexit module. */
 void _Py_PyAtExit(void (*func)(PyObject *), PyObject *module)
 {
-    PyThreadState *ts;
-    PyInterpreterState *is;
-
-    ts = PyThreadState_GET();
-    is = ts->interp;
+    PyInterpreterState *is = _PyInterpreterState_Get();
 
     /* Guard against API misuse (see bpo-17852) */
     assert(is->pyexitfunc == NULL || is->pyexitfunc == func);
diff --git a/Python/pystate.c b/Python/pystate.c
index e8d390dfcfb..7a4cd48077f 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -264,6 +264,21 @@ PyInterpreterState_Delete(PyInterpreterState *interp)
 }
 
 
+PyInterpreterState *
+_PyInterpreterState_Get(void)
+{
+    PyThreadState *tstate = GET_TSTATE();
+    if (tstate == NULL) {
+        Py_FatalError("_PyInterpreterState_Get(): no current thread state");
+    }
+    PyInterpreterState *interp = tstate->interp;
+    if (interp == NULL) {
+        Py_FatalError("_PyInterpreterState_Get(): no current interpreter");
+    }
+    return interp;
+}
+
+
 int64_t
 PyInterpreterState_GetID(PyInterpreterState *interp)
 {
@@ -1184,10 +1199,9 @@ _check_xidata(_PyCrossInterpreterData *data)
 int
 _PyObject_GetCrossInterpreterData(PyObject *obj, _PyCrossInterpreterData *data)
 {
-    PyThreadState *tstate = PyThreadState_Get();
-    // PyThreadState_Get() aborts if lookup fails, so we don't need
+    // _PyInterpreterState_Get() aborts if lookup fails, so we don't need
     // to check the result for NULL.
-    PyInterpreterState *interp = tstate->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
 
     // Reset data before re-populating.
     *data = (_PyCrossInterpreterData){0};
@@ -1235,7 +1249,7 @@ _call_in_interpreter(PyInterpreterState *interp,
      * naive approach.
      */
     PyThreadState *save_tstate = NULL;
-    if (interp != PyThreadState_Get()->interp) {
+    if (interp != _PyInterpreterState_Get()) {
         // XXX Using the "head" thread isn't strictly correct.
         PyThreadState *tstate = PyInterpreterState_ThreadHead(interp);
         // XXX Possible GILState issues?
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index f6f06c7640a..273eae25e2e 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -92,7 +92,7 @@ PyRun_InteractiveLoopFlags(FILE *fp, const char *filename_str, PyCompilerFlags *
     PyCompilerFlags local_flags;
     int nomem_count = 0;
 #ifdef Py_REF_DEBUG
-    int show_ref_count = PyThreadState_GET()->interp->core_config.show_ref_count;
+    int show_ref_count = _PyInterpreterState_Get()->core_config.show_ref_count;
 #endif
 
     filename = PyUnicode_DecodeFSDefault(filename_str);
@@ -336,17 +336,13 @@ maybe_pyc_file(FILE *fp, const char* filename, const char* ext, int closeit)
 static int
 set_main_loader(PyObject *d, const char *filename, const char *loader_name)
 {
-    PyInterpreterState *interp;
-    PyThreadState *tstate;
     PyObject *filename_obj, *bootstrap, *loader_type = NULL, *loader;
     int result = 0;
 
     filename_obj = PyUnicode_DecodeFSDefault(filename);
     if (filename_obj == NULL)
         return -1;
-    /* Get current thread state and interpreter pointer */
-    tstate = PyThreadState_GET();
-    interp = tstate->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     bootstrap = PyObject_GetAttrString(interp->importlib,
                                        "_bootstrap_external");
     if (bootstrap != NULL) {
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index b6c816e9f62..177b8307626 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -56,51 +56,55 @@ _Py_IDENTIFIER(write);
 PyObject *
 _PySys_GetObjectId(_Py_Identifier *key)
 {
-    PyThreadState *tstate = PyThreadState_GET();
-    PyObject *sd = tstate->interp->sysdict;
-    if (sd == NULL)
+    PyObject *sd = _PyInterpreterState_GET_UNSAFE()->sysdict;
+    if (sd == NULL) {
         return NULL;
+    }
     return _PyDict_GetItemId(sd, key);
 }
 
 PyObject *
 PySys_GetObject(const char *name)
 {
-    PyThreadState *tstate = PyThreadState_GET();
-    PyObject *sd = tstate->interp->sysdict;
-    if (sd == NULL)
+    PyObject *sd = _PyInterpreterState_GET_UNSAFE()->sysdict;
+    if (sd == NULL) {
         return NULL;
+    }
     return PyDict_GetItemString(sd, name);
 }
 
 int
 _PySys_SetObjectId(_Py_Identifier *key, PyObject *v)
 {
-    PyThreadState *tstate = PyThreadState_GET();
-    PyObject *sd = tstate->interp->sysdict;
+    PyObject *sd = _PyInterpreterState_GET_UNSAFE()->sysdict;
     if (v == NULL) {
-        if (_PyDict_GetItemId(sd, key) == NULL)
+        if (_PyDict_GetItemId(sd, key) == NULL) {
             return 0;
-        else
+        }
+        else {
             return _PyDict_DelItemId(sd, key);
+        }
     }
-    else
+    else {
         return _PyDict_SetItemId(sd, key, v);
+    }
 }
 
 int
 PySys_SetObject(const char *name, PyObject *v)
 {
-    PyThreadState *tstate = PyThreadState_GET();
-    PyObject *sd = tstate->interp->sysdict;
+    PyObject *sd = _PyInterpreterState_GET_UNSAFE()->sysdict;
     if (v == NULL) {
-        if (PyDict_GetItemString(sd, name) == NULL)
+        if (PyDict_GetItemString(sd, name) == NULL) {
             return 0;
-        else
+        }
+        else {
             return PyDict_DelItemString(sd, name);
+        }
     }
-    else
+    else {
         return PyDict_SetItemString(sd, name, v);
+    }
 }
 
 static PyObject *
@@ -626,9 +630,13 @@ sys_setcheckinterval(PyObject *self, PyObject *args)
                      "are deprecated.  Use sys.setswitchinterval() "
                      "instead.", 1) < 0)
         return NULL;
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
-    if (!PyArg_ParseTuple(args, "i:setcheckinterval", &interp->check_interval))
+
+    int check_interval;
+    if (!PyArg_ParseTuple(args, "i:setcheckinterval", &check_interval))
         return NULL;
+
+    PyInterpreterState *interp = _PyInterpreterState_Get();
+    interp->check_interval = check_interval;
     Py_RETURN_NONE;
 }
 
@@ -647,7 +655,7 @@ sys_getcheckinterval(PyObject *self, PyObject *args)
                      "are deprecated.  Use sys.getswitchinterval() "
                      "instead.", 1) < 0)
         return NULL;
-    PyInterpreterState *interp = PyThreadState_GET()->interp;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
     return PyLong_FromLong(interp->check_interval);
 }
 
@@ -1154,12 +1162,10 @@ static PyObject *
 sys_setdlopenflags(PyObject *self, PyObject *args)
 {
     int new_val;
-    PyThreadState *tstate = PyThreadState_GET();
     if (!PyArg_ParseTuple(args, "i:setdlopenflags", &new_val))
         return NULL;
-    if (!tstate)
-        return NULL;
-    tstate->interp->dlopenflags = new_val;
+    PyInterpreterState *interp = _PyInterpreterState_Get();
+    interp->dlopenflags = new_val;
     Py_RETURN_NONE;
 }
 
@@ -1176,10 +1182,8 @@ can be found in the os module (RTLD_xxx constants, e.g. os.RTLD_LAZY).");
 static PyObject *
 sys_getdlopenflags(PyObject *self, PyObject *args)
 {
-    PyThreadState *tstate = PyThreadState_GET();
-    if (!tstate)
-        return NULL;
-    return PyLong_FromLong(tstate->interp->dlopenflags);
+    PyInterpreterState *interp = _PyInterpreterState_Get();
+    return PyLong_FromLong(interp->dlopenflags);
 }
 
 PyDoc_STRVAR(getdlopenflags_doc,
diff --git a/Python/thread.c b/Python/thread.c
index 07743840693..a1e1fa64f12 100644
--- a/Python/thread.c
+++ b/Python/thread.c
@@ -92,7 +92,7 @@ PyThread_init_thread(void)
 size_t
 PyThread_get_stacksize(void)
 {
-    return PyThreadState_GET()->interp->pythread_stacksize;
+    return _PyInterpreterState_Get()->pythread_stacksize;
 }
 
 /* Only platforms defining a THREAD_SET_STACKSIZE() macro