William Marsden (15 September 1940 – 12 October 2019)[1] was a British diplomat who served as the United Kingdom's Ambassador to Argentina from 1997 to 2000,[2] and to Costa Rica and Nicaragua concurrently from 1989 to 1992. From 2001 his work was primarily concerned with nature conservation, and he latterly served as Chairman of the Chagos Conservation Trust.[3]