A boatswain's mate is a petty officer assisting the boatswain aboard ship.
Specifically, boatswain's mate may refer to:
Boatswain's mate (United States Navy), a job classification in the United States Navy Boatswain's mate (United States Coast Guard), a job classification in the United States Coast Guard Boatswain's mate (National Oceanic and Atmospheric Administration), a job classification in the United States National Oceanic and Atmospheric Administration Bootsmannsmaat, a historical naval rank in Austria, Germany, and Russia The Boatswain's Mate, a 1914 one-act opera by Ethel Smyth
See also Boatswain (disambiguation)