The Kingfisher class was a class of nine patrol sloops of the British Royal Navy built in three groups of three each during the 1930s, that saw service during World War II, mainly on East Coast convoys in the North Sea.

The Kingfisher class was an attempt to build a patrol vessel under 600 tons, due to the lack of clauses on vessels this size in the London Naval Treaty of 1930. It was intended it would escort coastal shipping in wartime. Its small size and short range that this entailed (it was based on a scaled-down destroyer) rendered it unsuitable for open ocean work. The design had a number of shortcomings. Constructed to full naval warship specifications and powered by geared steam turbine engines, it was designed to too high a standard and were unsuitable for mass production. The ships were armed with one 4-inch gun forward and depth charges aft, which severely limited their ability to defend themselves, let alone their charges.

The woeful lack of defensive armament was addressed early in the war by adding a multiple Vickers machine gun on the quarterdeck in the Kingfisher and Kittiwake groups, as per the Shearwaters. As they became available, two 20 mm Oerlikon cannons were added, on pedestal mounts on the deckhouse aft. Two additional 20 mm cannons were added later to replace the multiple machine gun.

Centimetric Radar Type 271 was added on the roof of the bridge as it became available, this was a target indication set capable of picking up the conning tower or even the periscope or snorkel of a submarine. Radar Type 286 air warning was added at the masthead on most ships. The ships that had the Mark V gun on the open mounting HA Mark III had a shield added to give the gun crews a measure of protection on the exposed fo'c'sle.

The first ship, Kingfisher, was ordered under the 1933 Programme on 15 December 1933 and built by the Fairfield Shipbuilding and Engineering Company. The next pair of ships were part of the six sloops of the 1934 Programme and ordered from Alexander Stephen and Sons on 21 March 1935. Kittiwake and Sheldrake were ordered on 21 January 1936 from John I. Thornycroft & Company under the 1935 Programme while Widgeon was ordered on 13 January 1937 from Yarrow Shipbuilders. A further three ships were ordered on 6 April 1938 with Shearwater built by J. Samuel White and Company and the other two built by William Denny and Brothers. Unlike the earlier vessels, these three ships were built with a quadruple 0.5-inch machine gun and featured a high-angle 4 inch gun capable of attacking aircraft.

Nicholas Monsarrat, the author of The Cruel Sea, served in two Kingfisher-class sloops: HMS Guillemot in 1942 as First Lieutenant, and HMS Shearwater in 1943 as Captain, after they had been reclassified as corvettes. HMS Dipper and HMS Winger were the fictional names he gave to these Kingfisher class corvettes in his stories East Coast Corvette (1943) and Corvette Command (1944), written during the war when security included ship's names.