Alan Campbell Don KCVO (3 January 1885 – 3 May 1966) was a trustee of the National Portrait Gallery, editor of the Scottish Book of Common Prayer, chaplain and secretary to Cosmo Lang, Archbishop of Canterbury, from 1931 to 1941, Chaplain to the Speaker of the House of Commons from 1936 to 1946 and Dean of Westminster from 1946 to 1959.