diff --git a/CHANGES/9309.bugfix.rst b/CHANGES/9309.bugfix.rst
new file mode 100644
index 00000000000..73870da1938
--- /dev/null
+++ b/CHANGES/9309.bugfix.rst
@@ -0,0 +1 @@
+Fixed assembling the :class:`~yarl.URL` for web requests when the host contains a non-default port or IPv6 address -- by :user:`bdraco`.
diff --git a/aiohttp/web_request.py b/aiohttp/web_request.py
index 91fc1f42bfe..62a08ea248b 100644
--- a/aiohttp/web_request.py
+++ b/aiohttp/web_request.py
@@ -431,6 +431,10 @@ def host(self) -> str:
         - overridden value by .clone(host=new_host) call.
         - HOST HTTP header
         - socket.getfqdn() value
+
+        For example, 'example.com' or 'localhost:8080'.
+
+        For historical reasons, the port number may be included.
         """
         host = self._message.headers.get(hdrs.HOST)
         if host is not None:
@@ -454,8 +458,10 @@ def remote(self) -> Optional[str]:
 
     @reify
     def url(self) -> URL:
-        url = URL.build(scheme=self.scheme, host=self.host)
-        return url.join(self._rel_url)
+        """The full URL of the request."""
+        # authority is used here because it may include the port number
+        # and we want yarl to parse it correctly
+        return URL.build(scheme=self.scheme, authority=self.host).join(self._rel_url)
 
     @reify
     def path(self) -> str:
diff --git a/tests/test_web_request.py b/tests/test_web_request.py
index ba12d6f54e7..9e613bb6613 100644
--- a/tests/test_web_request.py
+++ b/tests/test_web_request.py
@@ -526,6 +526,16 @@ def test_url_url() -> None:
     assert URL("http://example.com/path") == req.url
 
 
+def test_url_non_default_port() -> None:
+    req = make_mocked_request("GET", "/path", headers={"HOST": "example.com:8123"})
+    assert req.url == URL("http://example.com:8123/path")
+
+
+def test_url_ipv6() -> None:
+    req = make_mocked_request("GET", "/path", headers={"HOST": "[::1]:8123"})
+    assert req.url == URL("http://[::1]:8123/path")
+
+
 def test_clone() -> None:
     req = make_mocked_request("GET", "/path")
     req2 = req.clone()