A gun-brig was a small brig-rigged warship that enjoyed popularity in the Royal Navy during the Napoleonic Wars, during which large numbers were purchased or built.

The later gun-brigs developed from this beginning into smaller versions of the brig-sloops with increased draught and seaworthiness, but were less suited for inshore warfare.

The purpose-built gun-brigs were all established with a complement of 50 men, and maintained this level throughout their main period of operation, although the actual number carried varied with availability.

Few men in the Royal Navy had a good word to say for the gun-brigs, which rolled terribly and were greatly over-crowded, but they had to be employed.In this criticism of the gun-brig, Forester was perhaps being a little unfair; the class had been designed largely as convoy escorts for coastal operations and it is little wonder they rolled heavily in the open sea.

They performed sterling service in a wide range of conditions not envisaged by their designers, making them analogous in this respect to the Flower-class corvette of World War II; cheap, uncomfortable, over-crowded, and lightly armed but completely essential.

[Note 1] No further details were recorded, but their existence probably explains why the initial numbering of the Acute class below (prior to their being given names) began with GB No.

The first batch of twelve gun-brigs were all built by contract to a design by Surveyor of the Navy Sir John Henslow, and ordered on 6 March 1794; they were all named and registered on 26 May.

From March 1795 all twelve of the class were attached to the Inshore Squadron commanded by Captain Sir Sidney Smith.

The first ten of these small mercantile brigs were all purchased at Leith and fitted there for naval service, being registered on the Navy List on 5 April 1797.

Built in 1798 as a cutter, and re-rigged by the Navy as a brig, this was a very small vessel of only 60 tons, established with just 18 men and six 3-pounder guns.

In 1825 Malay pirates captured her and massacred her entire crew before wrecking her on Babar Island in the southern Moluccas.

As in 1797, the two Surveyors were asked to produce alternative designs for the next batch of gun-brigs, which were lengthened by five feet from the previous classes.

These assorted vessels did not constitute a single class, but as all were procured from the enemy during the French Revolutionary War they are here treated similarly.

[10] During the French Revolutionary War, two similar vessels were captured from the Dutch and commissioned in the Royal Navy as gun-brigs.

These vessels did not constitute a single class, but as both were procured from the enemy during the French Revolutionary War they are here treated similarly.

These four assorted vessels purchased in June 1804 did not constitute a single class, but as procured as a group they are here treated similarly.

Unlike earlier brigs of this size, most were re-rated as brig-sloops at or soon after their completion, and were under commanders (rather than lieutenants), at least until 1815–17, when they reverted to being gun-brigs.

These assorted vessels did not constitute a single class, but as all were procured from the enemy during the Napoleonic War they are here treated similarly.