Janus-class destroyer

Three Janus-class torpedo-boat destroyers (TBDs) served with the Royal Navy. HMS Janus (1895), HMS Lightning (1895) and HMS Porcupine (1895) were ordered under the 1893-94 Programme, all laid down on 28 March 1894 at Palmer's shipyard at Jarrow and launched during 1895. They displaced 275 tons (light), were 204 ft long and produced 3,900 hp from their Reed water tube boilers which gave them a top speed of 27 kn.

Under the 1893–1894 Naval Estimates, the British Admiralty placed orders for 36 torpedo-boat destroyers, all to be capable of 27 kn, the "27-knotters", as a follow-on to the six prototype "26-knotters" ordered in the previous 1892–1893 Estimates. As was typical for torpedo craft at the time, the Admiralty left detailed design to the builders, laying down only broad requirements.

In September 1913 the Admiralty re-classed all the remaining 27-knotter destroyers, including all three Janus-class vessels, as A Class destroyers.