HMS Theseus /ˈtʰeː.seu̯s/, [ˈt̪ʰeːs̠ɛu̯s̠] (R64) was a Colossus-class light fleet aircraft carrier of the Royal Navy. Theseus was laid down on 6 January 1943 by Fairfield at Govan, and was launched on 6 July 1944. She was involved in the Korean War and the Suez Crisis. The scrapping of the Theseus was commenced on 29 May 1962 at Inverkeithing, Scotland.

The 1942 Design Light Fleet Carrier, commonly referred to as the British Light Fleet Carrier, was a light aircraft carrier design created by the Royal Navy during the Second World War, and used by eight naval forces between 1944 and 2001. They were designed and constructed by civilian shipyards to serve as an intermediate step between the expensive, full-size fleet aircraft carriers and the less expensive but limited-capability escort carriers.