diff --git a/docs/cis-policy-mapping.md b/docs/cis-policy-mapping.md
index c01c8f9..b399082 100644
--- a/docs/cis-policy-mapping.md
+++ b/docs/cis-policy-mapping.md
@@ -12,8 +12,8 @@ and avoids applying workload admission rules to platform namespaces.
 | 5.2.7 | `require-non-root` | A Pod without explicit non-root execution is rejected. | Does not prove the image cannot switch users internally. |
 | 5.5.1 | `restrict-image-registries` | Images outside the approved registry set are rejected. | Full provenance needs signing, verification, and trusted build controls. |
 | 5.7.3 supplemental | `require-resource-limits` | Pods must declare CPU and memory limits. | Resource limits are a defense-in-depth control, not a direct CIS test. |
+| Supplemental | `disallow-default-namespace` | Common application resources in `default` are rejected. | Namespace hygiene is defense in depth, not a one-to-one CIS test. |
 
 The Kubernetes CIS Benchmark is broader than admission policy. kube-bench
 covers node, control-plane, RBAC, audit, network policy, and manual review
 areas that these Kyverno policies do not implement.
-
diff --git a/policies/README.md b/policies/README.md
index b0ffe88..943169a 100644
--- a/policies/README.md
+++ b/policies/README.md
@@ -1,11 +1,12 @@
 # Kyverno policy baseline
 
-These policies are `ClusterPolicy` resources, but they intentionally select
-only namespaces labeled `security-baseline/open: "true"`. That keeps the
-portfolio demo enforceable without blocking Kyverno, Falco, ArgoCD, or other
-platform components. Expand the label scope deliberately for a real cluster.
+These policies are `ClusterPolicy` resources. The workload hardening policies
+select only namespaces labeled `security-baseline/open: "true"`. The separate
+`disallow-default-namespace` policy specifically protects the Kubernetes
+`default` namespace. This keeps the portfolio demo enforceable without
+blocking Kyverno, Falco, ArgoCD, or other platform components.
 
-All five policies use `validationFailureAction: Enforce`, so a matching Pod is
+All six policies use `validationFailureAction: Enforce`, so a matching resource is
 rejected at admission time. The policies use `background: false` because the
 goal is to demonstrate admission enforcement, not retroactively evaluate
 existing objects.
@@ -16,9 +17,9 @@ existing objects.
 | `require-non-root` | 5.2.7 | Requires `runAsNonRoot: true` on containers and init containers. |
 | `require-resource-limits` | 5.7.3 supplemental | Requires CPU and memory limits. This is a supplemental control, not a one-to-one CIS test. |
 | `restrict-image-registries` | 5.5.1 supplemental | Allows only approved registries. Full image provenance requires signing and verification as well. |
+| `disallow-default-namespace` | Supplemental | Blocks common application resources from being created in `default`, which makes namespace ownership explicit. |
 | `disallow-host-network` | 5.2.3 and 5.2.5 | Rejects host PID, host network, and host IPC access. |
 
 The CIS benchmark includes manual checks and platform-specific exceptions.
 The mapping above describes the control objective each policy supports, not a
 claim that one Kyverno rule implements the entire benchmark control.
-
diff --git a/policies/kyverno/disallow-default-namespace.yaml b/policies/kyverno/disallow-default-namespace.yaml
new file mode 100644
index 0000000..dfcb8e9
--- /dev/null
+++ b/policies/kyverno/disallow-default-namespace.yaml
@@ -0,0 +1,41 @@
+apiVersion: kyverno.io/v1
+kind: ClusterPolicy
+metadata:
+  name: disallow-default-namespace
+  annotations:
+    policies.kyverno.io/title: Disallow application workloads in default
+    policies.kyverno.io/category: Namespace hygiene
+    policies.kyverno.io/severity: medium
+    # Supplemental namespace-isolation control. This is not a one-to-one CIS control.
+    policies.kyverno.io/cis-control: "supplemental"
+spec:
+  validationFailureAction: Enforce
+  background: false
+  failurePolicy: Fail
+  rules:
+    - name: application-resources-not-in-default
+      match:
+        any:
+          - resources:
+              kinds:
+                - Pod
+                - Deployment
+                - StatefulSet
+                - DaemonSet
+                - Job
+                - CronJob
+                - ReplicaSet
+                - ReplicationController
+                - Service
+                - Ingress
+              namespaceSelector:
+                matchLabels:
+                  kubernetes.io/metadata.name: default
+      validate:
+        message: Application resources must be deployed into an explicitly named namespace.
+        deny:
+          conditions:
+            any:
+              - key: "{{ request.namespace }}"
+                operator: Equals
+                value: default
diff --git a/policies/kyverno/kustomization.yaml b/policies/kyverno/kustomization.yaml
index c98c436..76d91be 100644
--- a/policies/kyverno/kustomization.yaml
+++ b/policies/kyverno/kustomization.yaml
@@ -7,3 +7,4 @@ resources:
   - require-resource-limits.yaml
   - restrict-image-registries.yaml
   - disallow-host-network.yaml
+  - disallow-default-namespace.yaml