In cyber security, a demilitarised zone (DMZ) is a subnetwork which separates the internal local area network (LAN) from untrusted external networks.

The external-facing servers, resources and services sit in the DMZ, meaning that they have accessible from and have access to the internet in addition to the other parts of the internal LAN. This means there is no direct access between the internet and the internal LAN cannot be reached.

Examples of services that might be located in the DMZ include e-mail, Web and Domain Name System (DNS) servers.