The RFA (Royal Fleet Auxiliary) Sir Tristram belongs to the auxiliary (ships of the) Royal Fleet, which consists of ships of general support of the combat units of the Royal Navy, equipped with fuels, spare parts, ammunition, food and water. She is a round-table class landing operations support ship, which was converted into a special forces training vessel in 2008. She was launched in 1966 and joined the British Navy in 1967. From completion to early 1970 RFA Sir Tristram was managed by British India Steam Navigation Company. In January 1972 RFA Sir Tristram was part of a special force against the invasion off British Honduras together with HMS Fearless, RFA Sir Bedivere and RFA Sir Geraint. In 1977 RFA Sir Tristram was used for the accommodation of guests at the Queen’s inspection of the fleet in celebration of the 25th anniversary of her reign (Queen’s Silver Jubilee Fleet Review) in Spithead, UK.

In April 1982 Sir Tristram was diverted from Belize in Falkland Islands in order to take part in the Corporate operation, the British operation to re-occupy the Falklands.

In June 8, whilst she transported men and equipment to Fitzroy Cove together with Sir Galahad, Sir Tristram was attacked by Argentine Air Force aircrafts, each one loaded with three 500-lb (230-kg) Mark-82 bombs. Approximately at 14:00 local time the decks were swept away by gunfire and two crew members were killed. A 500-lb bomb penetrated the deck, but did not explode immediately, allowing for the evacuation of the ship by the rest of the crew. After the explosion, Sir Tristram was abandoned. Immediately after the end of the operations, Sir Tristram was towed to Port Stanley where she was used as ship to accommodate soldiers. Then Sir Tristram returned to the United Kingdom in 1983.

After reconstruction, Sir Tristram returned to active service in 1985, and took part in the Gulf War and the Balkan conflicts of the 1990s. The ship supported relief operations for the Mitch Hurricane off the coast of Central America. In 2000 the ship was deployed to Sierra Leone in order to support the British operations there, and followed a mission to the Baltic Sea in order to support mine countermeasure vessels. In early 2001 Sir Tristram returned to Sierra Leone in order to take over from RFA Sir Percivale as support ship of the British army forces there. In 2003 the ship was deployed as part of the British fleet in support of the invasion operations in Iraq.

The ship was decommissioned on 17 December 2005, but she continues to be used for training purposes by the Special Operations Command and the Special Forces of the United Kingdom. She is now based at the Portland naval station.