HMS A2 was an A-class submarine built for the Royal Navy in the first decade of the 20th century.

A2 was a member of the first British class of submarines, although slightly larger, faster and more heavily armed than the lead ship, HMS A1.

[1] For surface running, the boats were powered by a single 16-cylinder 450-brake-horsepower (336 kW) Wolseley petrol engine that drove one propeller shaft.

On the surface, A2 had a range of 320 nautical miles (590 km; 370 mi) at 10 knots (19 km/h; 12 mph);[1] submerged the boat had a range of 30 nautical miles (56 km; 35 mi) at 5 knots (9.3 km/h; 5.8 mph).

[1] Construction started in 1902 and the submarine was launched on 15 April 1903 and completed on 26 March 1904.