Victor Alexander Sereld Hay, 21st Earl of Erroll and 4th Baron Kilmarnock, KCMG (17 October 1876 – 20 February 1928), styled Lord Hay from 1876 to 1891 and Lord Kilmarnock from 1891 to 1927, was a British diplomat, a writer and briefly a member of the House of Lords, who was "noted for his tact and charm."