HMS Trenchant was a Trafalgar-class nuclear-powered fleet submarine of the Royal Navy built by Vickers Shipbuilding, Barrow-in-Furness.

She was laid down by Vickers Shipbuilding on 28 October 1985, and was launched on 3 November 1986 in the presence of Vice Admiral Sir Arthur Hezlet, who had commanded the World War II T-class submarine Trenchant.

[8] While approaching Fremantle, Western Australia, the submarine remained at a depth of 200 metres (660 ft) and grounded when she made contact with the continental shelf, coming to rest on a sloping patch of seafloor.

[citation needed] On 21 June 2007, the submarine became the first Royal Navy vessel to fire the new Block IV Tomahawk cruise missile in a live-firing trial in the Gulf of Mexico off the United States coast.

[11] During this time the vessel visited six different ports: Fujairah, UAE; the British Indian Ocean Territory – Diego Garcia; the Kingdom of Bahrain; Aqaba, Jordan; Souda Bay, Crete; and Gibraltar.

[20] Trenchant's final four-month deployment in the Atlantic was filmed for a Channel 5 television documentary called Submarine: Life Beneath the Waves, which was first shown in the United Kingdom in September 2021.