The ONC Prison is a prison owned by the Ordinance Nationality Corporation and is located along the shores near an ocean. It is first seen in Imprisoned and is the location of where Nash, Seal, and the Sandbox Reds and Blues are taken for questioning. The prison contains a room supposedly used for questioning and torture, a hangar bay, and a docking bay. Apparently, the prison can only be accessed via aircraft or boat as Seal, Nash, and the Sandbox troops are brought to the prison via Hornets while Allan, Mickey, and Bartholomew arrived on a pair of dinghies.
- The ONC prison is represented by the Halo 3 maps Foundry and Longshore.