diff --git a/changelog.d/20231204_142753_rra_DM_41998.md b/changelog.d/20231204_142753_rra_DM_41998.md
new file mode 100644
index 000000000..acd3a8a7f
--- /dev/null
+++ b/changelog.d/20231204_142753_rra_DM_41998.md
@@ -0,0 +1,3 @@
+### New features
+
+- An ingress may now be restricted to a specific user by setting the `username` attribute in the `config` section of a `GafaelfawrIngress`, or the corresponding `username` query parameter to the `/auth` route. Any other user will receive a 403 error. The scope requiremments must also still be met.
diff --git a/crds/ingress.yaml b/crds/ingress.yaml
index d81837e8f..89d7ddbe2 100644
--- a/crds/ingress.yaml
+++ b/crds/ingress.yaml
@@ -172,6 +172,13 @@ spec:
                             - true
                       required:
                         - anonymous
+                username:
+                  type: string
+                  description: >-
+                    Restrict access to this ingress to the given username. All
+                    other users, regardless of their scopes, will receive 403
+                    errors. The user's token must still satisfy any scope
+                    constraints.
             template:
               type: object
               description: "The template used to create the ingress."
diff --git a/docs/user-guide/gafaelfawringress.rst b/docs/user-guide/gafaelfawringress.rst
index 369b72317..e0b5c6538 100644
--- a/docs/user-guide/gafaelfawringress.rst
+++ b/docs/user-guide/gafaelfawringress.rst
@@ -196,6 +196,19 @@ The same token will also still be passed in the ``X-Auth-Request-Token`` header.
 
 If this configuration option is set, the incoming ``Authorization`` header will be entirely replaced by one containing only the delegated token, unlike Gafaelfawr's normal behavior of preserving any incoming ``Authorization`` header that doesn't include a Gafaelfawr token.
 
+Per-user ingresses
+==================
+
+Access to an ingress may be restricted to a specific user as follows:
+
+.. code-block:: yaml
+
+   config:
+     username: <username>
+
+Any user other than the one with the username ``<username>`` will then receive a 403 error.
+The scope requirements must still be met to allow access.
+
 .. _anonymous:
 
 Anonymous ingresses
diff --git a/docs/user-guide/manual-ingress.rst b/docs/user-guide/manual-ingress.rst
index 52b2f721c..e2b10ce72 100644
--- a/docs/user-guide/manual-ingress.rst
+++ b/docs/user-guide/manual-ingress.rst
@@ -203,4 +203,9 @@ Most but not all of these are discussed above.
     If set to a true value, replace the ``Authorization`` header with one containing the delegated token as a bearer token.
     This option only makes sense in combination with ``notebook`` or ``delegate_to``.
 
+``username`` (optional)
+    If set, access to this ingress is restricted to the specified user.
+    Any other user will receive a 403 error.
+    ``scope`` must still be set and its requirements are still enforced.
+
 These parameters must be URL-encoded as GET parameters to the ``/auth`` route.
diff --git a/src/gafaelfawr/handlers/auth.py b/src/gafaelfawr/handlers/auth.py
index 38ec38cca..170a587e5 100644
--- a/src/gafaelfawr/handlers/auth.py
+++ b/src/gafaelfawr/handlers/auth.py
@@ -62,6 +62,9 @@ class AuthConfig:
     use_authorization: bool
     """Whether to put any delegated token in the ``Authorization`` header."""
 
+    username: str | None
+    """Restrict access to the ingress to only this username."""
+
 
 def auth_uri(
     x_original_uri: (str | None) = Header(
@@ -152,6 +155,17 @@ def auth_config(
         ),
         examples=[True],
     ),
+    username: str | None = Query(
+        None,
+        title="Restrict to username",
+        description=(
+            "Only allow access to this ingress by the user with the given"
+            " username. All other users, regardless of scopes, will receive"
+            " 403 errors. The user must still meet the scope requirements"
+            " for the ingress."
+        ),
+        examples=["rra"],
+    ),
     auth_uri: str = Depends(auth_uri),
     context: RequestContext = Depends(context_dependency),
 ) -> AuthConfig:
@@ -174,6 +188,8 @@ def auth_config(
         required_scopes=sorted(scopes),
         satisfy=satisfy.name.lower(),
     )
+    if username:
+        context.rebind_logger(required_user=username)
 
     if delegate_scope:
         delegate_scopes = {s.strip() for s in delegate_scope.split(",")}
@@ -193,6 +209,7 @@ def auth_config(
         delegate_scopes=delegate_scopes,
         minimum_lifetime=lifetime,
         use_authorization=use_authorization,
+        username=username,
     )
 
 
@@ -308,6 +325,16 @@ async def get_auth(
             auth_config.scopes,
         )
 
+    # Check a user constraint. InsufficientScopeError is not really correct,
+    # but none of the RFC 6750 error codes are correct and it's the closest.
+    if auth_config.username and token_data.username != auth_config.username:
+        raise generate_challenge(
+            context,
+            auth_config.auth_type,
+            InsufficientScopeError("Access not allowed for this user"),
+            auth_config.scopes,
+        )
+
     # Log and return the results.
     context.logger.info("Token authorized")
     headers = await build_success_headers(context, auth_config, token_data)
diff --git a/src/gafaelfawr/models/kubernetes.py b/src/gafaelfawr/models/kubernetes.py
index cea23839f..f5482a1ae 100644
--- a/src/gafaelfawr/models/kubernetes.py
+++ b/src/gafaelfawr/models/kubernetes.py
@@ -273,6 +273,9 @@ class GafaelfawrIngressConfig(CamelCaseModel):
     )
     """The scopes to require for access."""
 
+    username: str | None = None
+    """Restrict access to the given user."""
+
     @model_validator(mode="after")
     def _validate_conflicts(self) -> Self:
         """Check for conflicts between settings.
@@ -288,7 +291,13 @@ def _validate_conflicts(self) -> Self:
             raise ValueError(msg)
 
         if self.scopes and self.scopes.is_anonymous():
-            fields = ("auth_type", "delegate", "login_redirect", "replace_403")
+            fields = (
+                "auth_type",
+                "delegate",
+                "login_redirect",
+                "replace_403",
+                "username",
+            )
             for snake_name in fields:
                 if getattr(self, snake_name, None):
                     camel_name = to_camel_case(snake_name)
@@ -326,6 +335,8 @@ def to_auth_url(self) -> str:
                 query.append(("use_authorization", "true"))
         if self.auth_type:
             query.append(("auth_type", self.auth_type.value))
+        if self.username:
+            query.append(("username", self.username))
         return f"{base_url}/auth?" + urlencode(query)
 
 
diff --git a/tests/data/kubernetes/input/ingresses.yaml b/tests/data/kubernetes/input/ingresses.yaml
index f080fdd48..bd202fcbe 100644
--- a/tests/data/kubernetes/input/ingresses.yaml
+++ b/tests/data/kubernetes/input/ingresses.yaml
@@ -155,3 +155,29 @@ template:
                   name: something
                   port:
                     name: http
+---
+apiVersion: gafaelfawr.lsst.io/v1alpha1
+kind: GafaelfawrIngress
+metadata:
+  name: username-ingress
+  namespace: {namespace}
+config:
+  baseUrl: "https://foo.example.com"
+  scopes:
+    all: ["read:all"]
+  username: some-user
+template:
+  metadata:
+    name: username
+  spec:
+    rules:
+      - host: foo.example.com
+        http:
+          paths:
+            - path: /foo
+              pathType: Prefix
+              backend:
+                service:
+                  name: something
+                  port:
+                    name: http
diff --git a/tests/data/kubernetes/output/ingresses.yaml b/tests/data/kubernetes/output/ingresses.yaml
index 071b83fc5..d4aa95f8b 100644
--- a/tests/data/kubernetes/output/ingresses.yaml
+++ b/tests/data/kubernetes/output/ingresses.yaml
@@ -195,3 +195,41 @@ spec:
                 port:
                   name: http
 status: {any}
+---
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: username
+  namespace: {namespace}
+  annotations:
+    nginx.ingress.kubernetes.io/auth-method: GET
+    nginx.ingress.kubernetes.io/auth-response-headers: "Authorization,Cookie,X-Auth-Request-Email,X-Auth-Request-Token,X-Auth-Request-User"
+    nginx.ingress.kubernetes.io/auth-url: "https://foo.example.com/auth?scope=read%3Aall&username=some-user"
+    nginx.ingress.kubernetes.io/configuration-snippet: |
+      {snippet}
+  creationTimestamp: {any}
+  generation: {any}
+  managedFields: {any}
+  ownerReferences:
+    - apiVersion: gafaelfawr.lsst.io/v1alpha1
+      blockOwnerDeletion: true
+      controller: true
+      kind: GafaelfawrIngress
+      name: username-ingress
+      uid: {any}
+  resourceVersion: {any}
+  uid: {any}
+spec:
+  ingressClassName: nginx
+  rules:
+    - host: foo.example.com
+      http:
+        paths:
+          - path: /foo
+            pathType: Prefix
+            backend:
+              service:
+                name: something
+                port:
+                  name: http
+status: {any}
diff --git a/tests/handlers/auth_test.py b/tests/handlers/auth_test.py
index f8d23106c..86b1e721d 100644
--- a/tests/handlers/auth_test.py
+++ b/tests/handlers/auth_test.py
@@ -1037,3 +1037,29 @@ async def test_ldap_error(
     # We should not report any error message to Slack, however. If we did, we
     # would risk drowning the alert channel during an LDAP outage.
     assert mock_slack.messages == []
+
+
+@pytest.mark.asyncio
+async def test_user(client: AsyncClient, factory: Factory) -> None:
+    token_data = await create_session_token(
+        factory, group_names=["admin"], scopes=["read:all"]
+    )
+
+    r = await client.get(
+        "/auth",
+        params={"scope": "read:all", "username": token_data.username},
+        headers={"Authorization": f"Bearer {token_data.token}"},
+    )
+    assert r.status_code == 200
+    assert r.headers["X-Auth-Request-User"] == token_data.username
+
+    r = await client.get(
+        "/auth",
+        params={"scope": "read:all", "username": "other-user"},
+        headers={"Authorization": f"Bearer {token_data.token}"},
+    )
+    assert r.status_code == 403
+    authenticate = parse_www_authenticate(r.headers["WWW-Authenticate"])
+    assert isinstance(authenticate, AuthErrorChallenge)
+    assert authenticate.auth_type == AuthType.Bearer
+    assert authenticate.error == AuthError.insufficient_scope