The Trafalgar is essentially a refinement of the Swiftsure class and designed six years later than its predecessor. The design included a new reactor core and the Type 2020 sonar.

Internal layout is almost identical to the Swiftsure, and it is only 2.5 metres longer.

The Trafalgar class have strengthened fins and retractable hydroplanes, allowing them to surface through thick ice.

The hull is also covered in anechoic tiles which are designed to absorb sound rather than reflect it, making the boats more difficult to detect with active sonar.

The major change was in propulsion. Rather than the seven/nine-bladed propeller used by the Swiftsures, Trafalgar class submarines use pump-jet propulsion - a high-pitch, low-revolution propeller which is much quieter but much heavier than conventional propeller designs. Development of this system was not complete in time for installation in the class's name-ship vessel, HMS Trafalgar, and so the pump-jet was first used in the second in the class, HMS Turbulent.

The first Trafalgar class submarine was ordered on April 7, 1977 and completed in 1983. Turbulent was ordered on July 28, 1978; Tireless on July 5, 1979; Torbay on June 26, 1981; Trenchant on March 22, 1983; Talent on September 10, 1984; and finally Triumph on July 3, 1986.

In 1993 Triumph sailed to Australia, covering a distance of 41,000 miles whilst submerged and without any forward support. This marked the longest solo deployment by any British nuclear submarine.

The Trafalgar class was to be replaced by the Future Attack Submarine (FASM), however this project was effectively cancelled in 2001 and replaced by the Maritime Underwater Future Capability. It seems likely that the Astute class will replace the Trafalgar class as well as the Swiftsure class.