diff --git a/Doc/library/http.server.rst b/Doc/library/http.server.rst
@@ -167,6 +167,13 @@ provides three different variants:
       header (using :meth:`send_header`) in all of its responses to clients.
       For backwards compatibility, the setting defaults to ``'HTTP/1.0'``.
 
+   .. attribute:: default_content_type
+
+      Specifies the content-type header value sent when the mime-type cannot
+      be guessed from the file extension of the requested URL.
+      For backwards compatibility, the setting defaults to
+      ``'application/octet-stream'``.
+
    .. attribute:: MessageClass
 
       Specifies an :class:`email.message.Message`\ -like class to parse HTTP
@@ -462,6 +469,16 @@ following command runs an HTTP/1.1 conformant server::
 .. versionchanged:: 3.11
    Added the ``--protocol`` option.
 
+By default, the server uses the MIME type ``'application/octet-stream'`` for
+the ``content-type`` header when the content type cannot be guessed from the
+URL's extension (if any). The option ``--default-content-type`` overrides
+this default with one of the user's choosing::
+
+        python -m http.server --default-content-type text/html
+
+.. versionchanged:: 3.13
+   Added the ``--default-content-type`` option.
+
 .. class:: CGIHTTPRequestHandler(request, client_address, server)
 
    This class is used to serve either files or output of CGI scripts from the

diff --git a/Lib/http/server.py b/Lib/http/server.py
@@ -269,6 +269,7 @@ class BaseHTTPRequestHandler(socketserver.StreamRequestHandler):
     # the client gets back when sending a malformed request line.
     # Most web servers default to HTTP 0.9, i.e. don't send a status line.
     default_request_version = "HTTP/0.9"
+    default_content_type = "application/octet-stream"
 
     def parse_request(self):
         """Parse a request (internal).
@@ -907,7 +908,7 @@ def guess_type(self, path):
         guess, _ = mimetypes.guess_file_type(path)
         if guess:
             return guess
-        return 'application/octet-stream'
+        return self.default_content_type
 
 
 # Utilities for CGIHTTPRequestHandler
@@ -1263,14 +1264,16 @@ def _get_best_family(*address):
 
 def test(HandlerClass=BaseHTTPRequestHandler,
          ServerClass=ThreadingHTTPServer,
-         protocol="HTTP/1.0", port=8000, bind=None):
+         protocol="HTTP/1.0", port=8000, bind=None,
+         content_type=BaseHTTPRequestHandler.default_content_type):
     """Test the HTTP request handler class.
 
     This runs an HTTP server on port 8000 (or the port argument).
 
     """
     ServerClass.address_family, addr = _get_best_family(bind, port)
     HandlerClass.protocol_version = protocol
+    HandlerClass.default_content_type = content_type
     with ServerClass(addr, HandlerClass) as httpd:
         host, port = httpd.socket.getsockname()[:2]
         url_host = f'[{host}]' if ':' in host else host
@@ -1301,6 +1304,9 @@ def test(HandlerClass=BaseHTTPRequestHandler,
                         default='HTTP/1.0',
                         help='conform to this HTTP version '
                              '(default: %(default)s)')
+    parser.add_argument('--content-type',  # parsed into content_type
+                        default=BaseHTTPRequestHandler.default_content_type,
+                        help='sets default content type for unknown extensions')
     parser.add_argument('port', default=8000, type=int, nargs='?',
                         help='bind to this port '
                              '(default: %(default)s)')
@@ -1330,4 +1336,5 @@ def finish_request(self, request, client_address):
         port=args.port,
         bind=args.bind,
         protocol=args.protocol,
+        content_type=args.content_type
     )
diff --git a/Misc/NEWS.d/next/Library/2023-12-25-19-14-07.gh-issue-113471.ZQMpbI.rst b/Misc/NEWS.d/next/Library/2023-12-25-19-14-07.gh-issue-113471.ZQMpbI.rst
@@ -0,0 +1 @@
+Adds ability to set default content-type for no extension/unrecognized extension on :mod:`http.server` module.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Adds ability to set default content-type for no extension/unrecognized extension on :mod:`http.server` module.