diff --git a/google/oauth2/_client.py b/google/oauth2/_client.py
index 2f4e847..f819371 100644
--- a/google/oauth2/_client.py
+++ b/google/oauth2/_client.py
@@ -24,11 +24,9 @@
 """
 
 import datetime
+import http.client
 import json
-
-import six
-from six.moves import http_client
-from six.moves import urllib
+import urllib
 
 from google.auth import _helpers
 from google.auth import exceptions
@@ -120,7 +118,7 @@
         )
         response_data = json.loads(response_body)
 
-        if response.status == http_client.OK:
+        if response.status == http.client.OK:
             break
         else:
             error_desc = response_data.get("error_description") or ""
@@ -131,9 +129,9 @@
             ):
                 retry += 1
                 continue
-            return response.status == http_client.OK, response_data
+            return response.status == http.client.OK, response_data
 
-    return response.status == http_client.OK, response_data
+    return response.status == http.client.OK, response_data
 
 
 def _token_endpoint_request(
@@ -196,7 +194,7 @@
         access_token = response_data["access_token"]
     except KeyError as caught_exc:
         new_exc = exceptions.RefreshError("No access token in response.", response_data)
-        six.raise_from(new_exc, caught_exc)
+        raise new_exc from caught_exc
 
     expiry = _parse_expiry(response_data)
 
@@ -236,7 +234,7 @@
         id_token = response_data["id_token"]
     except KeyError as caught_exc:
         new_exc = exceptions.RefreshError("No ID token in response.", response_data)
-        six.raise_from(new_exc, caught_exc)
+        raise new_exc from caught_exc
 
     payload = jwt.decode(id_token, verify=False)
     expiry = datetime.datetime.utcfromtimestamp(payload["exp"])
@@ -265,7 +263,7 @@
         access_token = response_data["access_token"]
     except KeyError as caught_exc:
         new_exc = exceptions.RefreshError("No access token in response.", response_data)
-        six.raise_from(new_exc, caught_exc)
+        raise new_exc from caught_exc
 
     refresh_token = response_data.get("refresh_token", refresh_token)
     expiry = _parse_expiry(response_data)
diff --git a/google/oauth2/_client_async.py b/google/oauth2/_client_async.py
index cf51211..8849023 100644
--- a/google/oauth2/_client_async.py
+++ b/google/oauth2/_client_async.py
@@ -24,11 +24,9 @@
 """
 
 import datetime
+import http.client
 import json
-
-import six
-from six.moves import http_client
-from six.moves import urllib
+import urllib
 
 from google.auth import exceptions
 from google.auth import jwt
@@ -85,7 +83,7 @@
 
         response_data = json.loads(response_body)
 
-        if response.status == http_client.OK:
+        if response.status == http.client.OK:
             break
         else:
             error_desc = response_data.get("error_description") or ""
@@ -96,9 +94,9 @@
             ):
                 retry += 1
                 continue
-            return response.status == http_client.OK, response_data
+            return response.status == http.client.OK, response_data
 
-    return response.status == http_client.OK, response_data
+    return response.status == http.client.OK, response_data
 
 
 async def _token_endpoint_request(
@@ -161,7 +159,7 @@
         access_token = response_data["access_token"]
     except KeyError as caught_exc:
         new_exc = exceptions.RefreshError("No access token in response.", response_data)
-        six.raise_from(new_exc, caught_exc)
+        raise new_exc from caught_exc
 
     expiry = client._parse_expiry(response_data)
 
@@ -201,7 +199,7 @@
         id_token = response_data["id_token"]
     except KeyError as caught_exc:
         new_exc = exceptions.RefreshError("No ID token in response.", response_data)
-        six.raise_from(new_exc, caught_exc)
+        raise new_exc from caught_exc
 
     payload = jwt.decode(id_token, verify=False)
     expiry = datetime.datetime.utcfromtimestamp(payload["exp"])
diff --git a/google/oauth2/_id_token_async.py b/google/oauth2/_id_token_async.py
index ab681a9..a4a526d 100644
--- a/google/oauth2/_id_token_async.py
+++ b/google/oauth2/_id_token_async.py
@@ -58,12 +58,10 @@
 .. _CacheControl: https://cachecontrol.readthedocs.io
 """
 
+import http.client
 import json
 import os
 
-import six
-from six.moves import http_client
-
 from google.auth import environment_vars
 from google.auth import exceptions
 from google.auth import jwt
@@ -88,7 +86,7 @@
     """
     response = await request(certs_url, method="GET")
 
-    if response.status != http_client.OK:
+    if response.status != http.client.OK:
         raise exceptions.TransportError(
             "Could not fetch certificates at {}".format(certs_url)
         )
@@ -243,10 +241,10 @@
                 "GOOGLE_APPLICATION_CREDENTIALS is not valid service account credentials.",
                 caught_exc,
             )
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
 
-    # 2. Try to fetch ID token from metada server if it exists. The code works for GAE and
-    # Cloud Run metadata server as well.
+    # 2. Try to fetch ID token from metada server if it exists. The code works
+    # for GAE and Cloud Run metadata server as well.
     try:
         from google.auth import compute_engine
         from google.auth.compute_engine import _metadata
diff --git a/google/oauth2/_reauth_async.py b/google/oauth2/_reauth_async.py
index 09e0760..510578b 100644
--- a/google/oauth2/_reauth_async.py
+++ b/google/oauth2/_reauth_async.py
@@ -34,8 +34,6 @@
 
 import sys
 
-from six.moves import range
-
 from google.auth import exceptions
 from google.oauth2 import _client
 from google.oauth2 import _client_async
diff --git a/google/oauth2/challenges.py b/google/oauth2/challenges.py
index d0b070e..7756a80 100644
--- a/google/oauth2/challenges.py
+++ b/google/oauth2/challenges.py
@@ -20,8 +20,6 @@
 import getpass
 import sys
 
-import six
-
 from google.auth import _helpers
 from google.auth import exceptions
 
@@ -44,8 +42,7 @@
     return getpass.getpass(text)
 
 
-@six.add_metaclass(abc.ABCMeta)
-class ReauthChallenge(object):
+class ReauthChallenge(object, metaclass=abc.ABCMeta):
     """Base class for reauth challenges."""
 
     @property
diff --git a/google/oauth2/credentials.py b/google/oauth2/credentials.py
index 158249e..98fd71b 100644
--- a/google/oauth2/credentials.py
+++ b/google/oauth2/credentials.py
@@ -35,8 +35,6 @@
 import io
 import json
 
-import six
-
 from google.auth import _cloud_sdk
 from google.auth import _helpers
 from google.auth import credentials
@@ -336,7 +334,7 @@
             ValueError: If the info is not in the expected format.
         """
         keys_needed = set(("refresh_token", "client_id", "client_secret"))
-        missing = keys_needed.difference(six.iterkeys(info))
+        missing = keys_needed.difference(info)
 
         if missing:
             raise ValueError(
diff --git a/google/oauth2/id_token.py b/google/oauth2/id_token.py
index 540ccd1..25492ca 100644
--- a/google/oauth2/id_token.py
+++ b/google/oauth2/id_token.py
@@ -55,12 +55,10 @@
 .. _CacheControl: https://cachecontrol.readthedocs.io
 """
 
+import http.client
 import json
 import os
 
-import six
-from six.moves import http_client
-
 from google.auth import environment_vars
 from google.auth import exceptions
 from google.auth import jwt
@@ -97,7 +95,7 @@
     """
     response = request(certs_url, method="GET")
 
-    if response.status != http_client.OK:
+    if response.status != http.client.OK:
         raise exceptions.TransportError(
             "Could not fetch certificates at {}".format(certs_url)
         )
@@ -242,10 +240,10 @@
                 "GOOGLE_APPLICATION_CREDENTIALS is not valid service account credentials.",
                 caught_exc,
             )
-            six.raise_from(new_exc, caught_exc)
+            raise new_exc from caught_exc
 
-    # 2. Try to fetch ID token from metada server if it exists. The code works for GAE and
-    # Cloud Run metadata server as well.
+    # 2. Try to fetch ID token from metada server if it exists. The code
+    # works for GAE and Cloud Run metadata server as well.
     try:
         from google.auth import compute_engine
         from google.auth.compute_engine import _metadata
diff --git a/google/oauth2/reauth.py b/google/oauth2/reauth.py
index d914fe9..fc2629e 100644
--- a/google/oauth2/reauth.py
+++ b/google/oauth2/reauth.py
@@ -34,8 +34,6 @@
 
 import sys
 
-from six.moves import range
-
 from google.auth import exceptions
 from google.oauth2 import _client
 from google.oauth2 import challenges
diff --git a/google/oauth2/sts.py b/google/oauth2/sts.py
index ae3c014..9f2d68a 100644
--- a/google/oauth2/sts.py
+++ b/google/oauth2/sts.py
@@ -31,10 +31,9 @@
 .. _rfc8693 section 2.2.1: https://tools.ietf.org/html/rfc8693#section-2.2.1
 """
 
+import http.client
 import json
-
-from six.moves import http_client
-from six.moves import urllib
+import urllib
 
 from google.oauth2 import utils
 
@@ -146,7 +145,7 @@
         )
 
         # If non-200 response received, translate to OAuthError exception.
-        if response.status != http_client.OK:
+        if response.status != http.client.OK:
             utils.handle_error_response(response_body)
 
         response_data = json.loads(response_body)
diff --git a/google/oauth2/utils.py b/google/oauth2/utils.py
index 593f032..c57833d 100644
--- a/google/oauth2/utils.py
+++ b/google/oauth2/utils.py
@@ -45,8 +45,6 @@
 import enum
 import json
 
-import six
-
 from google.auth import exceptions
 
 
@@ -77,8 +75,7 @@
         self.client_secret = client_secret
 
 
-@six.add_metaclass(abc.ABCMeta)
-class OAuthClientAuthHandler(object):
+class OAuthClientAuthHandler(object, metaclass=abc.ABCMeta):
     """Abstract class for handling client authentication in OAuth-based
     operations.
     """