ship of the line, large, square-rigged warship, carrying from 70 to 140 guns on two or more completely armed gun decks. In the great naval wars of the 17th, 18th, and early 19th cent., ships of the line were the largest naval units employed. They passed from use with the advent of the ironclad and the battleship. One of the few remaining examples of a ship of the line is Lord Nelson's flagship, the H.M.S. Victory, which has been preserved at Portsmouth, England.

Type of sailing warship, the principal vessel of the West's great navies from the mid-17th to the mid-19th century. It evolved from a tactic in naval warfare known as the line of battle, in which two opposing columns of ships maneuvered to fire their guns broadside against each other. Since the largest ships carrying the biggest guns usually won these battles, this led to the construction of more big line-of-battle ships, or ships of the line. These three-masted ships were often 200 ft (60 m) long, displaced 1,200–2,000 tons (1,100–1,800 metric tons), and had crews of 600–800 men; they usually had 60–110 cannons and other guns arranged along three decks. They eventually gave way to the steam-powered battleship.

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