MacArthur "Mac" Foster (June 27, 1942 – July 19, 2010) was a 20th-century American heavyweight professional boxer. He competed from 1966 to 1976, winning 30 of his 36 professional bouts, with all his victories achieved by knockout. He stopped heavyweight contenders Thad Spencer, Cleveland Williams, whom he defeated twice, and Zora Folley. Foster went the distance against Muhammad Ali in April 1972, losing by a 15-round unanimous decision.