diff --git a/Doc/deprecations/pending-removal-in-3.15.rst b/Doc/deprecations/pending-removal-in-3.15.rst
@@ -35,7 +35,7 @@ Pending removal in Python 3.15

* :class:`locale`:

-  * The :func:`~locale.getdefaultlocale` function
    has been deprecated since Python 3.11.
    Its removal was originally planned for Python 3.13 (:gh:`90817`),
    but has been postponed to Python 3.15.

diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
@@ -1113,8 +1113,7 @@ conflict.
   components running in the same process (such as the GNU ``readline``
   library), the updated setting is also seen in subprocesses (regardless of
   whether or not those processes are running a Python interpreter), as well as
-   in operations that query the environment rather than the current C locale
-   (such as Python's own :func:`locale.getdefaultlocale`).

   Configuring one of these locales (either explicitly or via the above
   implicit locale coercion) automatically enables the ``surrogateescape``

@@ -1811,7 +1811,7 @@ Standard Library
  * :func:`!importlib.resources.read_text`
  * :func:`!importlib.resources.path`

-* The :func:`locale.getdefaultlocale` function is deprecated and will be
  removed in Python 3.15. Use :func:`locale.setlocale`,
  :func:`locale.getpreferredencoding(False) <locale.getpreferredencoding>` and
  :func:`locale.getlocale` functions instead.
@@ -2080,7 +2080,7 @@ Porting notes for the C API are

* :mod:`calendar`: The :class:`calendar.LocaleTextCalendar` and
  :class:`calendar.LocaleHTMLCalendar` classes now use
-  :func:`locale.getlocale`, instead of using :func:`locale.getdefaultlocale`,
  if no locale is specified.
  (Contributed by Victor Stinner in :issue:`46659`.)


@@ -121,6 +121,14 @@ Deprecated
Removed
=======

platform
--------


diff --git a/Lib/locale.py b/Lib/locale.py
@@ -23,7 +23,7 @@

# Yuck:  LC_MESSAGES is non-standard:  can't tell whether it exists before
# trying the import.  So __all__ is also fiddled at the end of the file.
-__all__ = ["getlocale", "getdefaultlocale", "getpreferredencoding", "Error",
           "setlocale", "localeconv", "strcoll", "strxfrm",
           "str", "atof", "atoi", "format_string", "currency",
           "normalize", "LC_CTYPE", "LC_COLLATE", "LC_TIME", "LC_MONETARY",
@@ -521,69 +521,6 @@ def _build_localename(localetuple):
        raise TypeError('Locale must be None, a string, or an iterable of '
                        'two strings -- language code, encoding.') from None

-def getdefaultlocale(envvars=('LC_ALL', 'LC_CTYPE', 'LANG', 'LANGUAGE')):
-
-    """ Tries to determine the default locale settings and returns
-        them as tuple (language code, encoding).
-
-        According to POSIX, a program which has not called
-        setlocale(LC_ALL, "") runs using the portable 'C' locale.
-        Calling setlocale(LC_ALL, "") lets it use the default locale as
-        defined by the LANG variable. Since we don't want to interfere
-        with the current locale setting we thus emulate the behavior
-        in the way described above.
-
-        To maintain compatibility with other platforms, not only the
-        LANG variable is tested, but a list of variables given as
-        envvars parameter. The first found to be defined will be
-        used. envvars defaults to the search path used in GNU gettext;
-        it must always contain the variable name 'LANG'.
-
-        Except for the code 'C', the language code corresponds to RFC
-        1766.  code and encoding can be None in case the values cannot
-        be determined.
-
-    """
-
-    import warnings
-    warnings._deprecated(
-        "locale.getdefaultlocale",
-        "{name!r} is deprecated and slated for removal in Python {remove}. "
-        "Use setlocale(), getencoding() and getlocale() instead.",
-        remove=(3, 15))
-    return _getdefaultlocale(envvars)
-
-
-def _getdefaultlocale(envvars=('LC_ALL', 'LC_CTYPE', 'LANG', 'LANGUAGE')):
-    try:
-        # check if it's supported by the _locale module
-        import _locale
-        code, encoding = _locale._getdefaultlocale()
-    except (ImportError, AttributeError):
-        pass
-    else:
-        # make sure the code/encoding values are valid
-        if sys.platform == "win32" and code and code[:2] == "0x":
-            # map windows language identifier to language name
-            code = windows_locale.get(int(code, 0))
-        # ...add other platform-specific processing here, if
-        # necessary...
-        return code, encoding
-
-    # fall back on POSIX behaviour
-    import os
-    lookup = os.environ.get
-    for variable in envvars:
-        localename = lookup(variable,None)
-        if localename:
-            if variable == 'LANGUAGE':
-                localename = localename.split(':')[0]
-            break
-    else:
-        localename = 'C'
-    return _parse_localename(localename)
-
-
def getlocale(category=LC_CTYPE):

    """ Returns the current setting for the given locale category as
@@ -1728,12 +1665,11 @@ def _init_categories(categories=categories):
    _init_categories()
    del categories['LC_ALL']

-    print('Locale defaults as determined by getdefaultlocale():')
    print('-'*72)
-    lang, enc = getdefaultlocale()
-    print('Language: ', lang or '(undefined)')
-    print('Encoding: ', enc or '(undefined)')
-    print()

    print('Locale settings on startup:')
    print('-'*72)

diff --git a/Lib/test/test_locale.py b/Lib/test/test_locale.py
@@ -483,30 +483,6 @@ def test_japanese(self):


class TestMiscellaneous(unittest.TestCase):
-    def test_defaults_UTF8(self):
-        # Issue #18378: on (at least) macOS setting LC_CTYPE to "UTF-8" is
-        # valid. Furthermore LC_CTYPE=UTF is used by the UTF-8 locale coercing
-        # during interpreter startup (on macOS).
-        import _locale
-
-        self.assertEqual(locale._parse_localename('UTF-8'), (None, 'UTF-8'))
-
-        if hasattr(_locale, '_getdefaultlocale'):
-            orig_getlocale = _locale._getdefaultlocale
-            del _locale._getdefaultlocale
-        else:
-            orig_getlocale = None
-
-        try:
-            with os_helper.EnvironmentVarGuard() as env:
-                env.unset('LC_ALL', 'LC_CTYPE', 'LANG', 'LANGUAGE')
-                env.set('LC_CTYPE', 'UTF-8')
-
-                with check_warnings(('', DeprecationWarning)):
-                    self.assertEqual(locale.getdefaultlocale(), (None, 'UTF-8'))
-        finally:
-            if orig_getlocale is not None:
-                _locale._getdefaultlocale = orig_getlocale

    def test_getencoding(self):
        # Invoke getencoding to make sure it does not cause exceptions.

diff --git a/Misc/NEWS.d/next/Library/2025-05-17-09-09-00.gh-issue-134086.asfhs.rst b/Misc/NEWS.d/next/Library/2025-05-17-09-09-00.gh-issue-134086.asfhs.rst
@@ -0,0 +1 @@
diff --git a/Modules/_localemodule.c b/Modules/_localemodule.c
@@ -444,50 +444,6 @@ _locale_strxfrm_impl(PyObject *module, PyObject *str)
}
#endif

-#if defined(MS_WINDOWS)
-
-/*[clinic input]
-_locale._getdefaultlocale
-
-[clinic start generated code]*/
-
-static PyObject *
-_locale__getdefaultlocale_impl(PyObject *module)
-/*[clinic end generated code: output=e6254088579534c2 input=003ea41acd17f7c7]*/
-{
-    char encoding[20];
-    char locale[100];
-
-    PyOS_snprintf(encoding, sizeof(encoding), "cp%u", GetACP());
-
-    if (GetLocaleInfoA(LOCALE_USER_DEFAULT,
-                      LOCALE_SISO639LANGNAME,
-                      locale, sizeof(locale))) {
-        Py_ssize_t i = strlen(locale);
-        locale[i++] = '_';
-        if (GetLocaleInfoA(LOCALE_USER_DEFAULT,
-                          LOCALE_SISO3166CTRYNAME,
-                          locale+i, (int)(sizeof(locale)-i)))
-            return Py_BuildValue("ss", locale, encoding);
-    }
-
-    /* If we end up here, this windows version didn't know about
-       ISO639/ISO3166 names (it's probably Windows 95).  Return the
-       Windows language identifier instead (a hexadecimal number) */
-
-    locale[0] = '0';
-    locale[1] = 'x';
-    if (GetLocaleInfoA(LOCALE_USER_DEFAULT, LOCALE_IDEFAULTLANGUAGE,
-                      locale+2, sizeof(locale)-2)) {
-        return Py_BuildValue("ss", locale, encoding);
-    }
-
-    /* cannot determine the language code (very unlikely) */
-    Py_INCREF(Py_None);
-    return Py_BuildValue("Os", Py_None, encoding);
-}
-#endif
-
#ifdef HAVE_LANGINFO_H
#define LANGINFO(X, Y) {#X, X, Y}
static struct langinfo_constant{
@@ -899,9 +855,6 @@ static struct PyMethodDef PyLocale_Methods[] = {
#ifdef HAVE_WCSXFRM
    _LOCALE_STRXFRM_METHODDEF
#endif
-#if defined(MS_WINDOWS)
-    _LOCALE__GETDEFAULTLOCALE_METHODDEF
-#endif
#ifdef HAVE_LANGINFO_H
    _LOCALE_NL_LANGINFO_METHODDEF
#endif

diff --git a/Modules/clinic/_localemodule.c.h b/Modules/clinic/_localemodule.c.h
-Original file line number
+Diff line change
@@ Expand Up / @@ -121,6 +121,14 @@ Deprecated @@
     Removed
     =======
     platform
     --------
@@ Expand Down @@