diff --git a/Doc/library/http.client.rst b/Doc/library/http.client.rst
index f0da8ee..ae6c91f 100644
--- a/Doc/library/http.client.rst
+++ b/Doc/library/http.client.rst
@@ -339,6 +339,15 @@
 | :const:`UPGRADE_REQUIRED`                | ``426`` | HTTP Upgrade to TLS,                                                  |
 |                                          |         | :rfc:`2817`, Section 6                                                |
 +------------------------------------------+---------+-----------------------------------------------------------------------+
+| :const:`PRECONDITION_REQUIRED`           | ``428`` | Additional HTTP Status Codes,                                         |
+|                                          |         | :rfc:`6585`, Section 3                                                |
++------------------------------------------+---------+-----------------------------------------------------------------------+
+| :const:`TOO_MANY_REQUESTS`               | ``429`` | Additional HTTP Status Codes,                                         |
+|                                          |         | :rfc:`6585`, Section 4                                                |
++------------------------------------------+---------+-----------------------------------------------------------------------+
+| :const:`REQUEST_HEADER_FIELDS_TOO_LARGE` | ``431`` | Additional HTTP Status Codes,                                         |
+|                                          |         | :rfc:`6585`, Section 5                                                |
++------------------------------------------+---------+-----------------------------------------------------------------------+
 | :const:`INTERNAL_SERVER_ERROR`           | ``500`` | HTTP/1.1, `RFC 2616, Section                                          |
 |                                          |         | 10.5.1                                                                |
 |                                          |         | <http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.5.1>`_  |
@@ -369,6 +378,12 @@
 | :const:`NOT_EXTENDED`                    | ``510`` | An HTTP Extension Framework,                                          |
 |                                          |         | :rfc:`2774`, Section 7                                                |
 +------------------------------------------+---------+-----------------------------------------------------------------------+
+| :const:`NETWORK_AUTHENTICATION_REQUIRED` | ``511`` | Additional HTTP Status Codes,                                         |
+|                                          |         | :rfc:`6585`, Section 6                                                |
++------------------------------------------+---------+-----------------------------------------------------------------------+
+
+  .. versionchanged:: 3.3
+     Added codes ``428``, ``429``, ``431`` and ``511`` from :rfc:`6585`.
 
 
 .. data:: responses
diff --git a/Lib/http/client.py b/Lib/http/client.py
index 9c110d5..6089192 100644
--- a/Lib/http/client.py
+++ b/Lib/http/client.py
@@ -141,6 +141,9 @@
 LOCKED = 423
 FAILED_DEPENDENCY = 424
 UPGRADE_REQUIRED = 426
+PRECONDITION_REQUIRED = 428
+TOO_MANY_REQUESTS = 429
+REQUEST_HEADER_FIELDS_TOO_LARGE = 431
 
 # server error
 INTERNAL_SERVER_ERROR = 500
@@ -151,6 +154,7 @@
 HTTP_VERSION_NOT_SUPPORTED = 505
 INSUFFICIENT_STORAGE = 507
 NOT_EXTENDED = 510
+NETWORK_AUTHENTICATION_REQUIRED = 511
 
 # Mapping status codes to official W3C names
 responses = {
@@ -192,6 +196,9 @@
     415: 'Unsupported Media Type',
     416: 'Requested Range Not Satisfiable',
     417: 'Expectation Failed',
+    428: 'Precondition Required',
+    429: 'Too Many Requests',
+    431: 'Request Header Fields Too Large',
 
     500: 'Internal Server Error',
     501: 'Not Implemented',
@@ -199,6 +206,7 @@
     503: 'Service Unavailable',
     504: 'Gateway Timeout',
     505: 'HTTP Version Not Supported',
+    511: 'Network Authentication Required',
 }
 
 # maximal amount of data to read at one time in _safe_read
diff --git a/Lib/http/server.py b/Lib/http/server.py
index c1b0596..cb66f2b 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -573,7 +573,7 @@
 
     # Table mapping response codes to messages; entries have the
     # form {code: (shortmessage, longmessage)}.
-    # See RFC 2616.
+    # See RFC 2616 and 6585.
     responses = {
         100: ('Continue', 'Request received, please continue'),
         101: ('Switching Protocols',
@@ -628,6 +628,12 @@
               'Cannot satisfy request range.'),
         417: ('Expectation Failed',
               'Expect condition could not be satisfied.'),
+        428: ('Precondition Required',
+              'The origin server requires the request to be conditional.'),
+        429: ('Too Many Requests', 'The user has sent too many requests '
+              'in a given amount of time ("rate limiting").'),
+        431: ('Request Header Fields Too Large', 'The server is unwilling to '
+              'process the request because its header fields are too large.'),
 
         500: ('Internal Server Error', 'Server got itself in trouble'),
         501: ('Not Implemented',
@@ -638,6 +644,8 @@
         504: ('Gateway Timeout',
               'The gateway server did not receive a timely response'),
         505: ('HTTP Version Not Supported', 'Cannot fulfill request.'),
+        511: ('Network Authentication Required',
+              'The client needs to authenticate to gain network access.'),
         }
 
 
diff --git a/Misc/ACKS b/Misc/ACKS
index 2be4bf7..75b544e 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1129,6 +1129,7 @@
 Hirokazu Yamamoto
 Ka-Ping Yee
 Jason Yeo
+EungJun Yi
 Bob Yodlowski
 Danny Yoo
 George Yoshida
diff --git a/Misc/NEWS b/Misc/NEWS
index 418bfc3..d27640d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -34,6 +34,9 @@
 Library
 -------
 
+- Issue #14809: Add HTTP status codes introduced by RFC 6585 to http.server
+  and http.client. Patch by EungJun Yi.
+
 - Issue #14777: tkinter may return undecoded UTF-8 bytes as a string when
   accessing the Tk clipboard.  Modify clipboad_get() to first request type
   UTF8_STRING when no specific type is requested in an X11 windowing