HMS R12 was one of 10 R-class submarines built for the Royal Navy during the First World War.

On the surface, the R class had a range of 2,400 nautical miles (4,400 km; 2,800 mi) at 9 knots (17 km/h; 10 mph) and 60 nmi (110 km; 69 mi) at 5 knots (9.3 km/h; 5.8 mph) submerged.

[4] The boats were armed with six 18-inch (45 cm) torpedo tubes in the bow.

They were equipped with an array of five hydrophones in the bow to allow them to locate and engage targets while submerged.

[4] HMS R12 was laid down on 1 December 1917 by Cammell Laird at Birkenhead, launched on 9 April 1918 and commissioned on 29 October 1919.