Neptune was a Bucentaure-class 80-gun ship of the line of the French Navy. Built during the last years of the French Revolutionary Wars she was launched at the beginning of the Napoleonic Wars. Her brief career with the French included several major battles, though she spent the last 12 years of her life under the Spanish flag.

The Bucentaure class was a class of 80-gun French ships of the line built to a design by Jacques-Noël Sané from 1802 onwards, of which at least 29 were ordered but only 21 ships were launched. They were a development from his earlier Tonnant class.