A Mast is a large spar, or vertical post or pole, usually stepped to the keel, supported from falling over by the forestay to forward, backstay from aft, and shrouds from larboard (port) and starboard. The primary purpose of the mast to support yards and sails for wind propulsion.
- The tallest mast is the mainmast.
- The forwardmost mast on a ship with two or more masts is the foremast.
- The aftermost mast on a ship with three masts is the mizzenmast or simply mizzen.