HMS Stygian (pennant number P249) was a S-class submarine of the British Royal Navy, and the only ship so far to bear the name.

After an eventful career in the Pacific during the Second World War, she was sold to be broken up for scrap on 28 October 1949, and finally scrapped by Metal Industries of Ardgour in August 1950.

She was assigned to operate with the Eastern Fleet in the Pacific Ocean.

She also sank the Japanese auxiliary minesweeper Wa 104 (the former Dutch Djember) and damaged the Japanese auxiliary submarine chaser Cha 104 off Bali.

Stygian acted as tow for the midget submarine XE-3, when XE-3 attacked the Japanese cruiser Takao in Singapore Harbour in Operation Struggle.