HMS K12 was a K class submarine built by Armstrong Whitworth, Newcastle upon Tyne. She was laid down in October 1915 and commissioned in August 1917. K12 took part in the Battle of May Island, surviving the disastrous exercise. Then in 1924, K12 collided with K2. K2 smashed a hole in the forward casing of K12 while K2 buckled her bows for about six feet. K12 was scrapped in 1926 in Charlestown.