diff --git a/api/v1alpha1/istio_types.go b/api/v1alpha1/istio_types.go
index f4e492a2e..4c2b068c4 100644
--- a/api/v1alpha1/istio_types.go
+++ b/api/v1alpha1/istio_types.go
@@ -60,6 +60,7 @@ type IstioSpec struct {
 	// Namespace to which the Istio components should be installed.
 	// +operator-sdk:csv:customresourcedefinitions:type=spec,xDescriptors={"urn:alm:descriptor:io.kubernetes:Namespace"}
 	// +kubebuilder:default=istio-system
+	// +kubebuilder:validation:XValidation:rule="self == oldSelf",message="spec.namespace is immutable"
 	Namespace string `json:"namespace"`
 
 	// Defines the values to be passed to the Helm charts when installing Istio.
diff --git a/api/v1alpha1/istiorevision_types.go b/api/v1alpha1/istiorevision_types.go
index 289d2f067..6dc84355b 100644
--- a/api/v1alpha1/istiorevision_types.go
+++ b/api/v1alpha1/istiorevision_types.go
@@ -42,6 +42,7 @@ type IstioRevisionSpec struct {
 
 	// Namespace to which the Istio components should be installed.
 	// +operator-sdk:csv:customresourcedefinitions:type=spec,xDescriptors={"urn:alm:descriptor:io.kubernetes:Namespace"}
+	// +kubebuilder:validation:XValidation:rule="self == oldSelf",message="spec.namespace is immutable"
 	Namespace string `json:"namespace"`
 
 	// Defines the values to be passed to the Helm charts when installing Istio.
diff --git a/bundle/manifests/sailoperator.io_istiorevisions.yaml b/bundle/manifests/sailoperator.io_istiorevisions.yaml
index 0ef057f39..8cbab6aa3 100644
--- a/bundle/manifests/sailoperator.io_istiorevisions.yaml
+++ b/bundle/manifests/sailoperator.io_istiorevisions.yaml
@@ -75,6 +75,9 @@ spec:
               namespace:
                 description: Namespace to which the Istio components should be installed.
                 type: string
+                x-kubernetes-validations:
+                - message: spec.namespace is immutable
+                  rule: self == oldSelf
               type:
                 default: Local
                 description: Type indicates whether this revision represents a local
diff --git a/bundle/manifests/sailoperator.io_istios.yaml b/bundle/manifests/sailoperator.io_istios.yaml
index 17edac4d8..f1de0d59e 100644
--- a/bundle/manifests/sailoperator.io_istios.yaml
+++ b/bundle/manifests/sailoperator.io_istios.yaml
@@ -87,6 +87,9 @@ spec:
                 default: istio-system
                 description: Namespace to which the Istio components should be installed.
                 type: string
+                x-kubernetes-validations:
+                - message: spec.namespace is immutable
+                  rule: self == oldSelf
               profile:
                 description: |-
                   The built-in installation configuration profile to use.
diff --git a/chart/crds/sailoperator.io_istiorevisions.yaml b/chart/crds/sailoperator.io_istiorevisions.yaml
index 066d23473..34ad05953 100644
--- a/chart/crds/sailoperator.io_istiorevisions.yaml
+++ b/chart/crds/sailoperator.io_istiorevisions.yaml
@@ -75,6 +75,9 @@ spec:
               namespace:
                 description: Namespace to which the Istio components should be installed.
                 type: string
+                x-kubernetes-validations:
+                - message: spec.namespace is immutable
+                  rule: self == oldSelf
               type:
                 default: Local
                 description: Type indicates whether this revision represents a local
diff --git a/chart/crds/sailoperator.io_istios.yaml b/chart/crds/sailoperator.io_istios.yaml
index fa5b227ee..1554a4b35 100644
--- a/chart/crds/sailoperator.io_istios.yaml
+++ b/chart/crds/sailoperator.io_istios.yaml
@@ -87,6 +87,9 @@ spec:
                 default: istio-system
                 description: Namespace to which the Istio components should be installed.
                 type: string
+                x-kubernetes-validations:
+                - message: spec.namespace is immutable
+                  rule: self == oldSelf
               profile:
                 description: |-
                   The built-in installation configuration profile to use.