Class overview
Operators	Royal Navy
Preceded by	Baltimore class
Succeeded by	Hind class
Built	1744–1746
In commission	1744–1780
Completed	21
Lost	7
General characteristics (common design)
Type	Sloop-of-war
Tons burthen	268 77⁄94 bm
Length	91 ft 0 in (27.7 m) (gundeck) 74 ft 9 in (22.8 m) (keel)
Beam	26 ft 0 in (7.9 m)
Depth of hold	12 ft 0 in (3.66 m) (vessels without platform in hold); 6 ft 10 in (2.08 m) (vessels with platform in hold)
Sail plan	Snow brig
Complement	110 (raised to 125 when armament increased)
Armament	10 × 6-pounder guns (later increased to 14 x 6-pounder guns); also 14 x ½-pounder swivel guns

The Merlin class was a class of twenty-one sloops of wooden construction built for the Royal Navy between 1743 and 1746. They were all built by contract with commercial builders to a common design prepared by Jacob Acworth, the Surveyor of the Navy; however, there were small differences between individual vessels, with a platform deck being constructed in the hold in Swallow (i), Merlin, Raven and Swallow (ii), whereas the other seventeen had no platform deck and thus their depth in hold was thus nearly twice as much.

The Merlin class design was one of two standard designs to which all Royal Navy sloops were built between 1743 and 1748 (the other design being the Hind class designed by Acworth's colleague Joseph Allin), who was appointed to share the post of Surveyor with Acworth on 11 July 1745.

Although initially each was armed with ten 6-pounder guns, this class was built with seven pairs of gunports on the upper deck, enabling them to be re-armed with fourteen 6-pounders later in their careers.

The first two – Swallow and Merlin – were ordered on 7 July 1743 to be built to replace two ex-Spanish vessels (the Galgo and Peregrine's Prize, both captured in 1742, and put into service by the British). Two more vessels to the same design were ordered on 30 March 1744; another two were ordered five days later, four more followed on 23 May and three others were ordered later that year.

On 5 April 1745 five more were ordered – including a second Falcon (named to replace the first, captured in the same year) and a second Swallow (similarly to replace the first, wrecked in 1744) – and a single extra vessel was ordered on 11 April. A final pair were ordered on 9 January 1746.

List of corvette and sloop classes of the Royal Navy
Drake-class sloops (1740)
Wolf-class sloops (1741)
Baltimore-class sloops (1742)
Hind-class sloops - the other 'standard' sloop design of the 1743–1746 era.

• Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
• McLaughlan, Ian. The Sloop of War 1650–1763. Seaforth Publishing, 2014. ISBN 978-1-84832-187-8.
• Winfield, Rif. British Warships in the Age of Sail 1714–1792: Design, Construction, Careers and Fates. Seaforth Publishing, 2007. ISBN 978-1-84415-700-6.