diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index f97eb08..6894c7c 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -1117,7 +1117,7 @@
    instance; for example: ``BaseClass.__init__(self, [args...])``.
 
    Because :meth:`__new__` and :meth:`__init__` work together in constructing
-   objects (:meth:`__new__` to create it, and :meth:`__init__` to customise it),
+   objects (:meth:`__new__` to create it, and :meth:`__init__` to customize it),
    no non-``None`` value may be returned by :meth:`__init__`; doing so will
    cause a :exc:`TypeError` to be raised at runtime.
 
@@ -1637,7 +1637,7 @@
 executed in a new namespace and the class name is bound locally to the
 result of ``type(name, bases, namespace)``.
 
-The class creation process can be customised by passing the ``metaclass``
+The class creation process can be customized by passing the ``metaclass``
 keyword argument in the class definition line, or by inheriting from an
 existing class that included such an argument. In the following example,
 both ``MyClass`` and ``MySubclass`` are instances of ``Meta``::
diff --git a/Doc/whatsnew/2.0.rst b/Doc/whatsnew/2.0.rst
index 4d49af1..5bd12ba 100644
--- a/Doc/whatsnew/2.0.rst
+++ b/Doc/whatsnew/2.0.rst
@@ -166,7 +166,7 @@
 registering new encodings that are then available throughout a Python program.
 If an encoding isn't specified, the default encoding is usually 7-bit ASCII,
 though it can be changed for your Python installation by calling the
-``sys.setdefaultencoding(encoding)`` function in a customised version of
+``sys.setdefaultencoding(encoding)`` function in a customized version of
 :file:`site.py`.
 
 Combining 8-bit and Unicode strings always coerces to Unicode, using the default
@@ -1139,7 +1139,7 @@
   Unix, not to be confused with :program:`gzip`\ -format files (which are
   supported by the :mod:`gzip` module) (Contributed by James C. Ahlstrom.)
 
-* :mod:`imputil`: A module that provides a simpler way for writing customised
+* :mod:`imputil`: A module that provides a simpler way for writing customized
   import hooks, in comparison to the existing :mod:`ihooks` module.  (Implemented
   by Greg Stein, with much discussion on python-dev along the way.)
 
diff --git a/Lib/http/cookiejar.py b/Lib/http/cookiejar.py
index 4466d2e..6d4572a 100644
--- a/Lib/http/cookiejar.py
+++ b/Lib/http/cookiejar.py
@@ -833,7 +833,7 @@
     May also modify cookies, though this is probably a bad idea.
 
     The subclass DefaultCookiePolicy defines the standard rules for Netscape
-    and RFC 2965 cookies -- override that if you want a customised policy.
+    and RFC 2965 cookies -- override that if you want a customized policy.
 
     """
     def set_ok(self, cookie, request):
diff --git a/Lib/test/cfgparser.2 b/Lib/test/cfgparser.2
index 1646de8..cfcfef2 100644
--- a/Lib/test/cfgparser.2
+++ b/Lib/test/cfgparser.2
@@ -129,7 +129,7 @@
 # Unix users can map to different SMB User names
 ;  username map = /etc/samba/smbusers
 
-# Using the following line enables you to customise your configuration
+# Using the following line enables you to customize your configuration
 # on a per machine basis. The %m gets replaced with the netbios name
 # of the machine that is connecting
 ;   include = /etc/samba/smb.conf.%m
diff --git a/Lib/test/test_gdb.py b/Lib/test/test_gdb.py
index cd7d292..33d7dc5 100644
--- a/Lib/test/test_gdb.py
+++ b/Lib/test/test_gdb.py
@@ -91,7 +91,7 @@
     raise unittest.SkipTest("gdb not built with embedded python support")
 
 # Verify that "gdb" can load our custom hooks, as OS security settings may
-# disallow this without a customised .gdbinit.
+# disallow this without a customized .gdbinit.
 _, gdbpy_errors = run_gdb('--args', sys.executable)
 if "auto-loading has been declined" in gdbpy_errors:
     msg = "gdb security settings prevent use of custom hooks: "
diff --git a/Lib/unittest/test/test_discovery.py b/Lib/unittest/test/test_discovery.py
index bb196e6..8f4017f 100644
--- a/Lib/unittest/test/test_discovery.py
+++ b/Lib/unittest/test/test_discovery.py
@@ -275,7 +275,7 @@
         self.assertEqual(Module.load_tests_args,
                          [(loader, [], 'test*.py')])
 
-    def test_find_tests_customise_via_package_pattern(self):
+    def test_find_tests_customize_via_package_pattern(self):
         # This test uses the example 'do-nothing' load_tests from
         # https://docs.python.org/3/library/unittest.html#load-tests-protocol
         # to make sure that that actually works.
diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index c7cae2e..0749e90 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -1263,7 +1263,7 @@
  *    SyntaxError extends Exception
  */
 
-/* Helper function to customise error message for some syntax errors */
+/* Helper function to customize error message for some syntax errors */
 static int _report_missing_parentheses(PySyntaxErrorObject *self);
 
 static int
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index eedd7c3..9e35eb2 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -2068,7 +2068,7 @@
 
 Return a new list containing all items from the iterable in ascending order.
 
-A custom key function can be supplied to customise the sort order, and the
+A custom key function can be supplied to customize the sort order, and the
 reverse flag can be set to request the result in descending order.
 [end disabled clinic input]*/
 
@@ -2078,7 +2078,7 @@
 "\n"
 "Return a new list containing all items from the iterable in ascending order.\n"
 "\n"
-"A custom key function can be supplied to customise the sort order, and the\n"
+"A custom key function can be supplied to customize the sort order, and the\n"
 "reverse flag can be set to request the result in descending order.");
 
 #define BUILTIN_SORTED_METHODDEF    \