diff --git a/mealie/core/security/providers/openid_provider.py b/mealie/core/security/providers/openid_provider.py
index a1124d248..5cee3b613 100644
--- a/mealie/core/security/providers/openid_provider.py
+++ b/mealie/core/security/providers/openid_provider.py
@@ -16,8 +16,9 @@ class OpenIDProvider(AuthProvider[UserInfo]):
 
     _logger = root_logger.get_logger("openid_provider")
 
-    def __init__(self, session: Session, data: UserInfo) -> None:
+    def __init__(self, session: Session, data: UserInfo, use_default_groups: bool = False) -> None:
         super().__init__(session, data)
+        self.use_default_groups = use_default_groups
 
     def authenticate(self) -> tuple[str, timedelta] | None:
         """Attempt to authenticate a user given a username and password"""
@@ -51,6 +52,15 @@ class OpenIDProvider(AuthProvider[UserInfo]):
 
         is_admin = False
         if settings.OIDC_REQUIRES_GROUP_CLAIM:
+            # We explicitly allow the groups claim to be missing to account for the behaviour of some IdPs:
+            # https://github.com/keycloak/keycloak/issues/22340
+            # We still log a warning though
+            if settings.OIDC_GROUPS_CLAIM not in claims:
+                self._logger.warning(
+                    "[OIDC] claims did not include a %s claim%s",
+                    settings.OIDC_GROUPS_CLAIM,
+                    ", using an empty list as default" if self.use_default_groups else "",
+                )
             group_claim = claims.get(settings.OIDC_GROUPS_CLAIM, []) or []
             is_admin = settings.OIDC_ADMIN_GROUP in group_claim if settings.OIDC_ADMIN_GROUP else False
             is_valid_user = settings.OIDC_USER_GROUP in group_claim if settings.OIDC_USER_GROUP else True
@@ -111,6 +121,6 @@ class OpenIDProvider(AuthProvider[UserInfo]):
         settings = get_app_settings()
 
         claims = {settings.OIDC_NAME_CLAIM, "email", settings.OIDC_USER_CLAIM}
-        if settings.OIDC_REQUIRES_GROUP_CLAIM:
+        if settings.OIDC_REQUIRES_GROUP_CLAIM and not self.use_default_groups:
             claims.add(settings.OIDC_GROUPS_CLAIM)
         return claims
diff --git a/mealie/routes/auth/auth.py b/mealie/routes/auth/auth.py
index 593ebda89..73025933e 100644
--- a/mealie/routes/auth/auth.py
+++ b/mealie/routes/auth/auth.py
@@ -138,7 +138,7 @@ async def oauth_callback(request: Request, response: Response, session: Session
         try:
             logger.debug("[OIDC] Claims not present in the ID token, pulling user info")
             userinfo = await client.userinfo(token=token)
-            auth_provider = OpenIDProvider(session, userinfo)
+            auth_provider = OpenIDProvider(session, userinfo, use_default_groups=True)
             auth = auth_provider.authenticate()
         except MissingClaimException:
             auth = None
diff --git a/tests/unit_tests/core/security/providers/test_openid_provider.py b/tests/unit_tests/core/security/providers/test_openid_provider.py
index 0fcd92690..6b198a294 100644
--- a/tests/unit_tests/core/security/providers/test_openid_provider.py
+++ b/tests/unit_tests/core/security/providers/test_openid_provider.py
@@ -61,6 +61,49 @@ def test_missing_groups_claim(monkeypatch: MonkeyPatch):
         auth_provider.authenticate()
 
 
+def test_missing_groups_claim_admin(monkeypatch: MonkeyPatch):
+    monkeypatch.setenv("OIDC_ADMIN_GROUP", "mealie_admin")
+    get_app_settings.cache_clear()
+
+    data = {
+        "preferred_username": "dude1",
+        "email": "email@email.com",
+        "name": "Firstname Lastname",
+    }
+    auth_provider = OpenIDProvider(None, data)
+
+    with pytest.raises(MissingClaimException):
+        auth_provider.authenticate()
+
+
+def test_missing_groups_claim_with_default(monkeypatch: MonkeyPatch):
+    monkeypatch.setenv("OIDC_USER_GROUP", "mealie_user")
+    get_app_settings.cache_clear()
+
+    data = {
+        "preferred_username": "dude1",
+        "email": "email@email.com",
+        "name": "Firstname Lastname",
+    }
+    auth_provider = OpenIDProvider(None, data, True)
+
+    assert auth_provider.authenticate() is None
+
+
+def test_missing_groups_claim_admin_group_with_default(monkeypatch: MonkeyPatch, unique_user: TestUser):
+    monkeypatch.setenv("OIDC_ADMIN_GROUP", "mealie_admin")
+    get_app_settings.cache_clear()
+
+    data = {
+        "preferred_username": "dude1",
+        "email": unique_user.email,
+        "name": "Firstname Lastname",
+    }
+    auth_provider = OpenIDProvider(unique_user.repos.session, data, True)
+
+    assert auth_provider.authenticate() is not None
+
+
 def test_missing_user_group(monkeypatch: MonkeyPatch):
     monkeypatch.setenv("OIDC_USER_GROUP", "mealie_user")
     get_app_settings.cache_clear()