diff --git a/CHANGELOG.md b/CHANGELOG.md
index 312896ea..6414a57f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@ and this project adheres to
 ### Fixed
 
 - 🔐(backend) enforce object-level permission checks on room endpoint #959
+- 🔒️(backend) add application validation when consuming external JWT #963
 
 ## [1.5.0] - 2026-01-28
 
diff --git a/src/backend/core/external_api/authentication.py b/src/backend/core/external_api/authentication.py
index 03c4b253..2ff16e2c 100644
--- a/src/backend/core/external_api/authentication.py
+++ b/src/backend/core/external_api/authentication.py
@@ -10,6 +10,8 @@ import jwt as pyJwt
 from lasuite.oidc_resource_server.backend import ResourceServerBackend as LaSuiteBackend
 from rest_framework import authentication, exceptions
 
+from core.models import Application
+
 User = get_user_model()
 logger = logging.getLogger(__name__)
 
@@ -94,6 +96,18 @@ class ApplicationJWTAuthentication(authentication.BaseAuthentication):
             logger.warning("Missing 'client_id' in JWT payload")
             raise exceptions.AuthenticationFailed("Invalid token claims.")
 
+        try:
+            application = Application.objects.get(client_id=client_id)
+        except Application.DoesNotExist as e:
+            logger.warning("Application not found: %s", client_id)
+            raise exceptions.AuthenticationFailed("Application not found.") from e
+
+        if not application.active:
+            logger.warning(
+                "Inactive application attempted authentication: %s", client_id
+            )
+            raise exceptions.AuthenticationFailed("Application is disabled.")
+
         if not is_delegated:
             logger.warning("Token is not marked as delegated")
             raise exceptions.AuthenticationFailed("Invalid token type.")
diff --git a/src/backend/core/tests/test_external_api_rooms.py b/src/backend/core/tests/test_external_api_rooms.py
index 1fc8c276..7a6ae487 100644
--- a/src/backend/core/tests/test_external_api_rooms.py
+++ b/src/backend/core/tests/test_external_api_rooms.py
@@ -16,10 +16,7 @@ import responses
 from lasuite.oidc_resource_server.authentication import ResourceServerAuthentication
 from rest_framework.test import APIClient
 
-from core.factories import (
-    RoomFactory,
-    UserFactory,
-)
+from core.factories import ApplicationFactory, RoomFactory, UserFactory
 from core.models import ApplicationScope, RoleChoices, Room, RoomAccessLevel, User
 
 pytestmark = pytest.mark.django_db
@@ -30,12 +27,14 @@ def generate_test_token(user, scopes):
     now = datetime.now(timezone.utc)
     scope_string = " ".join(scopes)
 
+    application = ApplicationFactory()
+
     payload = {
         "iss": settings.APPLICATION_JWT_ISSUER,
         "aud": settings.APPLICATION_JWT_AUDIENCE,
         "iat": now,
         "exp": now + timedelta(seconds=settings.APPLICATION_JWT_EXPIRATION_SECONDS),
-        "client_id": "test-client-id",
+        "client_id": str(application.client_id),
         "scope": scope_string,
         "user_id": str(user.id),
         "delegated": True,
@@ -664,6 +663,7 @@ def test_api_rooms_token_scope_case_insensitive(settings):
     """Token's scope should be case-insensitive."""
     settings.APPLICATION_JWT_SECRET_KEY = "devKey"
     user = UserFactory()
+    application = ApplicationFactory()
 
     # Generate token with mixed-case scope "Rooms:List" to verify that scope
     # validation is case-insensitive (should match "rooms:list")
@@ -673,7 +673,7 @@ def test_api_rooms_token_scope_case_insensitive(settings):
         "aud": settings.APPLICATION_JWT_AUDIENCE,
         "iat": now,
         "exp": now + timedelta(hours=1),
-        "client_id": "test-client",
+        "client_id": str(application.client_id),
         "scope": "Rooms:List",  # Mixed case - should be accepted as "rooms:list"
         "user_id": str(user.id),
         "delegated": True,
@@ -695,6 +695,7 @@ def test_api_rooms_token_without_delegated_flag(settings):
     """Token without delegated flag should be rejected."""
     settings.APPLICATION_JWT_SECRET_KEY = "devKey"
     user = UserFactory()
+    application = ApplicationFactory()
 
     # Generate token without delegated flag
     now = datetime.now(timezone.utc)
@@ -703,7 +704,7 @@ def test_api_rooms_token_without_delegated_flag(settings):
         "aud": settings.APPLICATION_JWT_AUDIENCE,
         "iat": now,
         "exp": now + timedelta(hours=1),
-        "client_id": "test-client",
+        "client_id": str(application.client_id),
         "scope": "rooms:list",
         "user_id": str(user.id),
         "delegated": False,  # Not delegated
@@ -727,6 +728,7 @@ def test_api_rooms_token_invalid_signature(mock_rs_authenticate, settings):
     """Token signed with an invalid key should defer to the next authentication."""
     settings.APPLICATION_JWT_SECRET_KEY = "devKey"
     user = UserFactory()
+    application = ApplicationFactory()
 
     # Generate token without delegated flag
     now = datetime.now(timezone.utc)
@@ -735,7 +737,7 @@ def test_api_rooms_token_invalid_signature(mock_rs_authenticate, settings):
         "aud": settings.APPLICATION_JWT_AUDIENCE,
         "iat": now,
         "exp": now + timedelta(hours=1),
-        "client_id": "test-client",
+        "client_id": str(application.client_id),
         "scope": "rooms:list",
         "user_id": str(user.id),
         "delegated": True,
@@ -820,6 +822,7 @@ def test_api_rooms_token_missing_client_id(settings):
 def test_api_rooms_token_missing_user_id(settings):
     """Token without user_id should be rejected."""
     settings.APPLICATION_JWT_SECRET_KEY = "devKey"
+    application = ApplicationFactory()
 
     now = datetime.now(timezone.utc)
     payload = {
@@ -827,7 +830,7 @@ def test_api_rooms_token_missing_user_id(settings):
         "aud": settings.APPLICATION_JWT_AUDIENCE,
         "iat": now,
         "exp": now + timedelta(hours=1),
-        "client_id": "test-client",
+        "client_id": str(application.client_id),
         "scope": "rooms:list",
         "delegated": True,
         # Missing user_id
@@ -850,6 +853,7 @@ def test_api_rooms_token_invalid_audience(settings):
     """Token with an invalid audience should be rejected."""
     settings.APPLICATION_JWT_SECRET_KEY = "devKey"
     user = UserFactory()
+    application = ApplicationFactory()
 
     now = datetime.now(timezone.utc)
     payload = {
@@ -857,7 +861,7 @@ def test_api_rooms_token_invalid_audience(settings):
         "aud": "invalid-audience",
         "iat": now,
         "exp": now + timedelta(hours=1),
-        "client_id": "test-client",
+        "client_id": str(application.client_id),
         "user_id": str(user.id),
         "scope": "rooms:list",
         "delegated": True,
@@ -879,6 +883,7 @@ def test_api_rooms_token_invalid_audience(settings):
 def test_api_rooms_token_unknown_user(settings):
     """Token for unknown user should be rejected."""
     settings.APPLICATION_JWT_SECRET_KEY = "devKey"
+    application = ApplicationFactory()
 
     now = datetime.now(timezone.utc)
     payload = {
@@ -886,7 +891,7 @@ def test_api_rooms_token_unknown_user(settings):
         "aud": settings.APPLICATION_JWT_AUDIENCE,
         "iat": now,
         "exp": now + timedelta(hours=1),
-        "client_id": "test-client",
+        "client_id": str(application.client_id),
         "user_id": str(uuid.uuid4()),
         "scope": "rooms:list",
         "delegated": True,
@@ -905,6 +910,65 @@ def test_api_rooms_token_unknown_user(settings):
     assert "user not found." in str(response.data).lower()
 
 
+def test_api_rooms_token_unknown_application(settings):
+    """Token for unknown application should be rejected."""
+    settings.APPLICATION_JWT_SECRET_KEY = "devKey"
+
+    now = datetime.now(timezone.utc)
+    payload = {
+        "iss": settings.APPLICATION_JWT_ISSUER,
+        "aud": settings.APPLICATION_JWT_AUDIENCE,
+        "iat": now,
+        "exp": now + timedelta(hours=1),
+        "client_id": "unknown-client-id",
+        "user_id": str(uuid.uuid4()),
+        "scope": "rooms:list",
+        "delegated": True,
+    }
+    token = jwt.encode(
+        payload,
+        settings.APPLICATION_JWT_SECRET_KEY,
+        algorithm=settings.APPLICATION_JWT_ALG,
+    )
+
+    client = APIClient()
+    client.credentials(HTTP_AUTHORIZATION=f"Bearer {token}")
+    response = client.get("/external-api/v1.0/rooms/")
+
+    assert response.status_code == 401
+    assert "application not found." in str(response.data).lower()
+
+
+def test_api_rooms_token_inactive_application(settings):
+    """Token for inactive application should be rejected."""
+    settings.APPLICATION_JWT_SECRET_KEY = "devKey"
+    application = ApplicationFactory(active=False)
+
+    now = datetime.now(timezone.utc)
+    payload = {
+        "iss": settings.APPLICATION_JWT_ISSUER,
+        "aud": settings.APPLICATION_JWT_AUDIENCE,
+        "iat": now,
+        "exp": now + timedelta(hours=1),
+        "client_id": str(application.client_id),
+        "user_id": str(uuid.uuid4()),
+        "scope": "rooms:list",
+        "delegated": True,
+    }
+    token = jwt.encode(
+        payload,
+        settings.APPLICATION_JWT_SECRET_KEY,
+        algorithm=settings.APPLICATION_JWT_ALG,
+    )
+
+    client = APIClient()
+    client.credentials(HTTP_AUTHORIZATION=f"Bearer {token}")
+    response = client.get("/external-api/v1.0/rooms/")
+
+    assert response.status_code == 401
+    assert "application is disabled." in str(response.data).lower()
+
+
 @responses.activate
 def test_resource_server_creates_user_on_first_authentication(settings):
     """New user should be created during first authentication.