|Builders:||Palmers Shipbuilding and Iron Company, Jarrow|
|Preceded by:||Hardy class|
|Succeeded by:||Salmon class|
|Type:||Torpedo Boat Destroyer|
|Displacement:||275 long tons (279 t)|
|Beam:||19 feet 9 inches (6.02 m)|
|Draught:||8 feet (2.4 m)|
|Propulsion:||Reed boilers, 3,900 hp (2,908 kW)|
|Speed:||27 knots (50 km/h; 31 mph)|
Three Janus-class torpedo-boat destroyers (TBDs) served with the Royal Navy. Janus, Lightning and Porcupine 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 feet 6 inches (62.33 m) long and produced 3,900 hp (2,900 kW) from their Reed water tube boilers which gave them a top speed of 27 knots (50 km/h; 31 mph).
These vessels belonged to the "27-knotter" type of early TBD, of which thirty were built under this Programme; those that survived until 1913 (including all three Janus-class vessels) were re-classed as the 'A' Class at that date.