The 24-pounder long gun was a heavy calibre piece of artillery mounted on warships of the Age of Sail. 24-pounders were in service in the navies of France, Spain, Great Britain, the Netherlands, Sweden, and the United States. They were comparable to the Canon de 24 Gribeauval used by the French Army as its largest piece of siege artillery. 24-pounders were used as main guns on the heaviest frigates of the early 19th century and on fourth-rate ships of the line, on the second deck of first-rate ships of the line, and on the second deck of a few large third-rates.

A frigate is a type of warship. In different eras, the roles and capabilities of ships classified as frigates have varied.