diff --git a/CHANGES/9204.misc.rst b/CHANGES/9204.misc.rst
new file mode 100644
index 00000000000..da12a7df6f7
--- /dev/null
+++ b/CHANGES/9204.misc.rst
@@ -0,0 +1 @@
+Significantly speed up filtering cookies -- by :user:`bdraco`.
diff --git a/aiohttp/cookiejar.py b/aiohttp/cookiejar.py
index 9b7f38d6685..85fd7716b56 100644
--- a/aiohttp/cookiejar.py
+++ b/aiohttp/cookiejar.py
@@ -94,6 +94,9 @@ def __init__(
         self._cookies: DefaultDict[Tuple[str, str], SimpleCookie] = defaultdict(
             SimpleCookie
         )
+        self._morsel_cache: DefaultDict[Tuple[str, str], Dict[str, Morsel[str]]] = (
+            defaultdict(dict)
+        )
         self._host_only_cookies: Set[Tuple[str, str]] = set()
         self._unsafe = unsafe
         self._quote_cookie = quote_cookie
@@ -129,6 +132,7 @@ def clear(self, predicate: Optional[ClearCookiePredicate] = None) -> None:
         if predicate is None:
             self._expire_heap.clear()
             self._cookies.clear()
+            self._morsel_cache.clear()
             self._host_only_cookies.clear()
             self._expirations.clear()
             return
@@ -210,6 +214,7 @@ def _delete_cookies(self, to_del: List[Tuple[str, str, str]]) -> None:
         for domain, path, name in to_del:
             self._host_only_cookies.discard((domain, name))
             self._cookies[(domain, path)].pop(name, None)
+            self._morsel_cache[(domain, path)].pop(name, None)
             self._expirations.pop((domain, path, name), None)
 
     def _expire_cookie(self, when: float, domain: str, path: str, name: str) -> None:
@@ -285,7 +290,12 @@ def update_cookies(self, cookies: LooseCookies, response_url: URL = URL()) -> No
                 else:
                     cookie["expires"] = ""
 
-            self._cookies[(domain, path)][name] = cookie
+            key = (domain, path)
+            if self._cookies[key].get(name) != cookie:
+                # Don't blow away the cache if the same
+                # cookie gets set again
+                self._cookies[key][name] = cookie
+                self._morsel_cache[key].pop(name, None)
 
         self._do_expiration()
 
@@ -337,30 +347,33 @@ def filter_cookies(self, request_url: URL) -> "BaseCookie[str]":
         # Create every combination of (domain, path) pairs.
         pairs = itertools.product(domains, paths)
 
-        # Point 2: https://www.rfc-editor.org/rfc/rfc6265.html#section-5.4
-        cookies = itertools.chain.from_iterable(
-            self._cookies[p].values() for p in pairs
-        )
         path_len = len(request_url.path)
-        for cookie in cookies:
-            name = cookie.key
-            domain = cookie["domain"]
+        # Point 2: https://www.rfc-editor.org/rfc/rfc6265.html#section-5.4
+        for p in pairs:
+            for name, cookie in self._cookies[p].items():
+                domain = cookie["domain"]
 
-            if (domain, name) in self._host_only_cookies and domain != hostname:
-                continue
+                if (domain, name) in self._host_only_cookies and domain != hostname:
+                    continue
 
-            # Skip edge case when the cookie has a trailing slash but request doesn't.
-            if len(cookie["path"]) > path_len:
-                continue
+                # Skip edge case when the cookie has a trailing slash but request doesn't.
+                if len(cookie["path"]) > path_len:
+                    continue
 
-            if is_not_secure and cookie["secure"]:
-                continue
+                if is_not_secure and cookie["secure"]:
+                    continue
+
+                # We already built the Morsel so reuse it here
+                if name in self._morsel_cache[p]:
+                    filtered[name] = self._morsel_cache[p][name]
+                    continue
 
-            # It's critical we use the Morsel so the coded_value
-            # (based on cookie version) is preserved
-            mrsl_val = cast("Morsel[str]", cookie.get(cookie.key, Morsel()))
-            mrsl_val.set(cookie.key, cookie.value, cookie.coded_value)
-            filtered[name] = mrsl_val
+                # It's critical we use the Morsel so the coded_value
+                # (based on cookie version) is preserved
+                mrsl_val = cast("Morsel[str]", cookie.get(cookie.key, Morsel()))
+                mrsl_val.set(cookie.key, cookie.value, cookie.coded_value)
+                self._morsel_cache[p][name] = mrsl_val
+                filtered[name] = mrsl_val
 
         return filtered