Is it possible for an application in one namespace to access an application in another namespace within the same cluster?

Yes, in Kubernetes, one application in a namespace can access an application in another namespace within the same cluster.

This is usually done using the full DNS name of the service, which includes the namespace, for example:

http://service-name.namespace.svc.cluster.local

It is also important to ensure that:

• The service in the other namespace is accessible (no network policies blocking access)
• The application has the necessary permissions to interact, if RBAC mechanisms are used

Thus, namespaces isolate resources by default but do not completely block network access between them.