HMS K1 was a First World War steam turbine-propelled K-class submarine of the Royal Navy. K1 was sunk to prevent it being captured after colliding with K4 off the Danish coast. She had been patrolling on the surface as part of a flotilla of submarines operating in line ahead. The flotilla was led by the light cruiser Blonde, followed by K1, K3, K4, and K7. The crew survived and taken off by two cutters sent from HMS Blonde. The collision occurred at approx 17:35 and after consultation with the rescued submariner officers and concluding that the K1 could not be saved, Blonde opened fire with one of her 4 inch guns and sank the submarine with a few shells at 19:10 hours.