The HMS Ocean (L12) of the UK Royal Navy is a Amphibious assault ship, the only one in her class. She is designed to support amphibious landing operations and to support the staff of Commander UK Amphibious Force and Commander UK Landing Force.

She was constructed in the mid-1990s by Kværner (Govan) on the Clyde and fitted out at Barrow-in-Furness prior to first of class trials and subsequent acceptance in service.

She was commissioned in September 1998 at her home port Devonport, Plymouth, Devon.

Ocean was designed to provide the amphibious assault capabilities last offered by HMS Albion and Bulwark whilst in the Commando role. She can deploy an Embarked Military Force (EMF) of a Royal Marines Commando Group from 3 Commando Brigade supported by aviation and landing craft assets. The ships company includes 9 Assault Squadron from 1 Assault Group Royal Marines.

Ocean is also capable of limited Anti-Submarine Warfare activities, supporting afloat training and acting as a base facility for other embarked forces including Counter-terrorism units.
 

The air group of up to 12 Sea King HC-4 medium-lift helicopters, six Lynx AH-7 light-lift/anti-Tank helicopters, and four Mk5 landing craft is provided by the Commando Helicopter Force however she can also support the Westland WAH-64 Apache operated by the Army Air Corps and helicopters of the Royal Air Force including the Chinook.

Ocean can transport up to fifteen fixed wing Harrier aircraft of Joint Force Harrier in the ferry role, but is unable to operate as a fixed wing aircraft carrier.