The Royal Navy's largest ship, Devonport-based HMS Ocean, will remain in service, Defence Secretary Liam Fox has said.
The Strategic Defence and Security Review in October revealed HMS Ocean or aircraft carrier HMS Illustrious would be scrapped.
Mr Fox said HMS Illustrious would be withdrawn in 2014.
A Ministry of Defence study said amphibious assault ship HMS Ocean was the most effective helicopter platform.
A ministerial statement said HMS Illustrious would be withdrawn from service once HMS Ocean had been refitted.
Four Devonport-based frigates, HMS Chatham, Campbeltown, Cumberland and Cornwall will be withdrawn in 2011.
Chatham will be withdrawn from service at the end of January and Campbeltown and Cumberland will follow on 1 April.
HMS Cornwall will be withdrawn at the end of April once it has returned from a deployment to the Indian Ocean.
HMS Ocean, built in the mid 1990s, is designed to support amphibious landing operations.
Its secondary roles include training, anti-submarine warfare and a base for anti-terrorist operations.