HMS A11 was an A-class submarine built for the Royal Navy in the first decade of the 20th century.

A11 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 600-brake-horsepower (447 kW) Wolseley petrol engine that drove one propeller shaft.

[1] On the surface, A11 had a range of 500 nautical miles (930 km; 580 mi) at 10 knots (19 km/h; 12 mph); submerged the boat had a range of 30 nautical miles (56 km; 35 mi) at 5 knots (9.3 km/h; 5.8 mph).

[5] In February 1913, A11 was one of three submarines based at Lamlash on the Isle of Arran off the west coast of Scotland.