HMS Trenchant is a Trafalgar-class nuclear-powered fleet submarine of the Royal Navy built by Vickers Shipbuilding, Barrow-in-Furness. Trenchant is in service and is based at HMNB Devonport. She is the third vessel and the second submarine of the Royal Navy to be named for the characteristic of vigour and incisiveness.

The submarine was ordered on 22 March 1983. 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. She was commissioned into the Royal Navy on 14 January 1989.

Trenchant is scheduled to be decommissioned in 2019.