TT Seawise Giant—earlier Oppama; later Happy Giant, Jahre Viking, Knock Nevis, and Mont—was a ULCC supertanker and the longest self-propelled ship in history.

[6][7] In 2013 her overall length was surpassed by 30 m by the floating liquefied natural gas installation Shell Prelude (FLNG), a monohull barge design 488 m (1,601 ft) long and 600,000 tonnes displacement.

[8] The vessel was converted to a floating storage and offloading unit (FSO) in 2004, moored off the coast of Qatar in the Persian Gulf at the Al Shaheen Oil Field.

at Oppama shipyard in Yokosuka, Kanagawa, Japan, as a 418,611-ton Ultra Large Crude Carrier (ULCC).

[6] The shipyard exercised its right to sell the vessel and a deal was brokered with Hong Kong Orient Overseas Container Line founder C. Y. Tung to lengthen the ship by several metres and add 146,152 tonnes of cargo capacity through jumboisation.

When Seawise Giant was fully loaded, her 25 meter/81 foot draft was too deep for the ship to safely navigate the relatively shallow waters of the English Channel.

[15] Seawise Giant was damaged in 1988 during the Iran–Iraq War by an Iraqi Air Force attack while anchored off Larak Island, Iran on 14 May 1988 and carrying Iranian crude oil.

Fires ignited aboard the ship and on oil that escaped into the surrounding water, which blazed out of control.

[19] Shortly after the Iran–Iraq war ended, a Norwegian investment firm managed by Finanshuset bought the damaged vessel, which had by then been towed to a lay-up location off Labuan.

[6][19] Knock Nevis was renamed Mont and reflagged to Sierra Leone by new owners Amber Development for a final voyage to India where she was scrapped at Alang by Priya Blue Industries.

[25][26] Seawise Giant was featured on the BBC series Jeremy Clarkson's Extreme Machines while sailing as Jahre Viking.