The A class as designated in 1913 was a heterogeneous group of torpedo boat destroyers (TBDs) built for the Royal Navy in the mid-1890s. Some 42 vessels were constructed to the individual designs of their builders to meet Admiralty specifications, the only uniting feature being a specified top speed of 27 knots (50 km/h). In fact the initial six vessels were generally differentiated by a slightly lower speed and were often referred to as "26-knotters" to distinguish them from the following batch of thirty-six vessels; all fifteen surviving "27-knotter" vessels were classified by the Admiralty as the A class in 1913 to provide some system to the naming of HM destroyers. All of the "26-knotters" and most of the "27-knotters" had been lost or scrapped before the 1913 classification, but for convenience all 42 ships are listed below. The number of funnels varied from one to four. All vessels had a distinctive "turtleback" forecastle that was intended to clear water from the bow, but actually tended to dig the bow in to anything of a sea, resulting in a very wet conning position.

HMS Lightning was a Janus-class destroyer of the British Royal Navy, later designated an A-class destroyer, built by Palmers and launched in 1895.