diff --git a/oauthenticator/cilogon.py b/oauthenticator/cilogon.py
index 318fa451..b11739fc 100644
--- a/oauthenticator/cilogon.py
+++ b/oauthenticator/cilogon.py
@@ -192,15 +192,28 @@ def _validate_scope(self, proposal):
             Configuring this allows all users authenticating with this identity
             provider.
         * `allowed_domains`: list of strings
-            Configuring this together with a `username_claim` that is an email
-            address enables users to be allowed if their `username_claim` ends
-            with `@` followed by a domain in this list.
+            Allows users associated with a listed domain to sign in.
 
             Use of wildcards `*` and a bit more is supported via Python's
             `fnmatch` function since version 16.2. Setting `allowed_domains` to
             `["jupyter.org", "*.jupyter.org"]` would for example allow users
             with `jovyan@jupyter.org` or `jovyan@hub.jupyter.org` usernames.
 
+            The domain the user is associated with is based on the username by
+            default in version 16, but this can be reconfigured to be based on a
+            claim in the `userinfo` response via `allowed_domains_claim`. The
+            domain is treated case insensitive and can either be directly
+            specified by the claim's value or extracted from an email string.
+        * `allowed_domains_claim`: string (optional)
+            This configuration represents the claim in the `userinfo` response
+            to identify a domain that could allow a user to sign in via
+            `allowed_domains`.
+
+            The claim can defaults to the username claim in version 16, but this
+            will change to "email" in version 17.
+
+            .. versionadded:: 16.2
+
         .. versionchanged:: 15.0
 
            Changed format from a list to a dictionary.
@@ -396,8 +409,20 @@ async def check_allowed(self, username, auth_model):
 
         idp_allowed_domains = self.allowed_idps[user_idp].get("allowed_domains")
         if idp_allowed_domains:
-            unprocessed_username = self._user_info_to_unprocessed_username(user_info)
-            user_domain = unprocessed_username.split("@", 1)[1].lower()
+            idp_allowed_domains_claim = self.allowed_idps[user_idp].get(
+                "allowed_domains_claim"
+            )
+            if idp_allowed_domains_claim:
+                raw_user_domain = user_info.get(idp_allowed_domains_claim)
+                if not raw_user_domain:
+                    message = f"Configured allowed_domains_claim {idp_allowed_domains_claim} for {user_idp} was not found in the response {user_info.keys()}"
+                    self.log.error(message)
+                    raise web.HTTPError(500, message)
+            else:
+                raw_user_domain = self._user_info_to_unprocessed_username(user_info)
+
+            # refine a domain from a string that possibly looks like an email
+            user_domain = raw_user_domain.split("@")[-1].lower()
 
             for ad in idp_allowed_domains:
                 # fnmatch allow us to use wildcards like * and ?, but
diff --git a/oauthenticator/schemas/cilogon-schema.yaml b/oauthenticator/schemas/cilogon-schema.yaml
index fb791599..3b97ce53 100644
--- a/oauthenticator/schemas/cilogon-schema.yaml
+++ b/oauthenticator/schemas/cilogon-schema.yaml
@@ -13,6 +13,8 @@ properties:
     type: array
     items:
       type: string
+  allowed_domains_claim:
+    type: string
   username_derivation:
     type: object
     additionalProperties: false
diff --git a/oauthenticator/tests/test_cilogon.py b/oauthenticator/tests/test_cilogon.py
index b67b359a..d8f46c54 100644
--- a/oauthenticator/tests/test_cilogon.py
+++ b/oauthenticator/tests/test_cilogon.py
@@ -151,7 +151,7 @@ async def test_cilogon(
                 "username_derivation": {
                     "username_claim": "email",
                 },
-                "allowed_domains": ["allowed-domain.org"],
+                "allowed_domains": ["ALLOWED-domain.org"],
             },
             {},
             "user1@allowed-domain.org",
@@ -244,6 +244,20 @@ async def test_cilogon(
             True,
             None,
         ),
+        (
+            "B - allowed by allowed_domains and allowed_domains_claim",
+            {
+                "username_derivation": {
+                    "username_claim": "email",
+                },
+                "allowed_domains": ["allowed-domain.org", "*.allowed-domain.org"],
+                "allowed_domains_claim": "email",
+            },
+            {},
+            "user1@sub.allowed-domain.org",
+            True,
+            None,
+        ),
         # test of allowed_users and admin_users together with
         # username_derivation actions to verify the final usernames is what
         # matters when describing allowed_users and admin_users