The coxswain (pronounced cox'n; often called the cox) is the person in charge of a boat, particularly its navigation and steering. Most familiarly, the coxswain is the member of a rowing crew who sits in the stern facing forward, steers the boat, and directs the speed and rhythm of the rowers. However, the term can be used for the skipper of any small boat.

In the Royal Navy in the days of sail, the coxswain was a petty officer who commanded a captain's or admiral's barge. Later he was the senior chief petty officer aboard a smaller vessel such as a corvette or submarine who was responsible for the steering and also assumed the duties which would be performed by the chief boatswain's mate and master-at-arms aboard larger vessels.

In the U.S. Navy, a coxswain or cockswain was at first the swain (boy servant) in charge of the small cock or cockboat that was kept aboard a ship for its captain's use. In time, the coxswain became the helmsman of any boat, regardless of size.