USS Seawolf (SSN-21) is a nuclear-powered fast attack submarine and the lead ship of her class.

She is the fourth submarine of the United States Navy named for the seawolf.

The contract to build Seawolf was awarded to the Electric Boat Division of General Dynamics on 9 January 1989 and her keel was laid down on 25 October 1989.

The 7-year 9-month time period from keel laying to commissioning is the longest for a submarine in the U.S. Navy.

[12] Port calls included HMNB Clyde in Faslane Scotland, and Gibraltar, and briefly in Tromsø, Norway.