The County class was a class of British guided missile destroyers, the first such warships built by the Royal Navy. Designed specifically around the Seaslug anti-aircraft missile system, the primary role of these ships was area air defence around the aircraft carrier task force in the nuclear-war environment.

A guided-missile destroyer (DDG) is a destroyer whose primary armament is guided missiles so they can provide anti-aircraft warfare screening for the fleet. The NATO standard designation for these vessels is DDG, while destroyers which have a primary gun armament or a small number of anti-aircraft missiles sufficient only for point-defense are designated DD. Nations vary in their use of destroyer D designation in their hull pennant numbering, either prefixing or dropping it altogether.