The mast of a sailing ship is a tall, vertical, or near vertical, spar, or arrangement of spars, which supports the sails. Large ships have several masts, with the size and configuration depending on the style of ship.

Until the 20th century, ships' masts were wooden. Originally, they were formed from single piece of timber, typically the trunks of fir trees. From the 16th century, ships were often built of a size requiring masts taller and thicker than could be made from single tree trunks. On these larger ships, to achieve the required height, the masts were built from up to four sections (also called masts), known in order of rising height about the decks as the lower, top, topgallant and royal masts. Giving the lower sections sufficient thickness necessitated building them up from separate pieces of wood. Such a section was known as a made mast, as opposed to sections formed from single pieces of timber, which were known as pole masts.

In a three-masted, square-sail carrying ship, the masts, given their standard names in bow to stern (front to back) order, are: