Enfield Revolver is the name applied to two totally separate models of self-extracting British handgun designed and manufactured at the government-owned Royal Small Arms Factory in Enfield; initially the .476 calibre (actually 11.6 mm) Revolver Enfield Mk I/Mk II revolvers (from 1880–1889), and later the .38/200 calibre Enfield No. 2 Mk I (from 1932–1957).
After the First World War, it was decided by the British Government that a smaller and lighter .38 calibre (9.65 mm) sidearm firing a long, heavy 200 grain (13 g) soft lead bullet would be preferable to the large Webley service revolvers using the .455 calibre (11.6 mm) round. While the .455 had proven to be an effective weapon for stopping enemy soldiers, the recoil of the .455 cartridge complicated marksmanship training. The authorities began a search for a double-action revolver with less weight and recoil that could be quickly mastered by a minimally-trained soldier, with a good probability of hitting an enemy with the first shot at extremely close ranges. By using such a long, heavy, round-nose lead bullet in a .38 calibre cartridge, it was found that the bullet, being minimally stabilised for its weight and calibre, tended to 'keyhole' or tumble longitudinally when striking an object, theoretically increasing wounding and stopping ability of human targets at short ranges. At the time, the .38 calibre Smith & Wesson cartridge with 200-grain (13 g) lead bullet, known as the .38/200, was also a popular cartridge in civilian and police use (in the USA, the .38/200 or 380/200 was known as the .38 Super Police load).
Consequently, the British firm of Webley & Scott tendered their Webley Mk IV revolver in .38/200 calibre. Rather than adopting it, the British authorities took the design to the Government-run Royal Small Arms Factory at Enfield, and the Enfield factory came up with a revolver that was very similar to the Webley Mk IV .38, but internally slightly different. The Enfield-designed pistol was quickly accepted under the designation Revolver, No 2 Mk I, and was adopted in 1931, followed in 1938 by the Mk I* (spurless hammer, double action only), and finally the Mk I** (simplified for wartime production) in 1942. After the 1945, all those revolvers were recalled and converted into No.2 Mark 1* configuration.