In the rating system of the Royal Navy used to categorise sailing warships, a first rate was the designation for the largest ships of the line. Originating in the Jacobean era with the designation of Ships Royal capable of carrying at least 400 men, the size and establishment of first-rates evolved over the following 250 years to eventually denote ships of the line carrying at least 80 guns across three gundecks. By the end of the eighteenth century, a first-rate carried no fewer than 100 guns and more than 850 crew, and had a measurement (burthen) tonnage of some 2,000 tons.

The rating system of the Royal Navy and its predecessors was used by the Royal Navy between the beginning of the 17th century and the middle of the 19th century to categorise sailing warships, initially classing them according to their assigned complement of men, and later according to the number of their carriage-mounted guns. The rating system of the Royal Navy formally came to an end in the late 19th century by declaration of the Admiralty. The main cause behind this declaration focused on new types of gun, the introduction of steam propulsion and the use of iron and steel armour which made rating ships by the number of guns obsolete.