King William's College (nicknamed KWC or King Bill's; ) is an independent school for pupils aged 3 to 18, located near Castletown on the Isle of Man. It is a member of the International Baccalaureate and Headmasters' and Headmistresses' Conference organisations. The College operates at two sites in or near Castletown: a main senior school campus on the shore of Castletown Bay, and a prep school (called The Buchan School) in the Westhill part of Castletown, two miles from the main campus. The College was originally for boys only, but became co-educational in the 1980s. It has roughly five hundred pupils, many from beyond the British Isles.