British Submarine HMS K4

HMS K4 was a K-class submarine of the British Royal Navy. Launched on 13 July 1916, she was commissioned on 1 January 1917.

K4 had an accident prone career, first being stranded on Walney Island in January 1917, followed by a collision with HMS K1 on 17 November 1917. This resulted in the loss of K1 although her crew were rescued.

On 31 January 1918, during a night time fleet exercise K4 was sunk after colliding with K6 and K7, while she was attempting to avoid K3. HMS K4 was lost with all hands.