Arena football is a variety of gridiron football. It is a proprietary game (the rights to which are owned by Gridiron Enterprises) played indoors on a smaller field than American or Canadian outdoor football, resulting in a faster and higher-scoring game. The sport was invented in 1981 (1981 in sports), and patented in 1987 (1987 in sports), by James F. Foster, Jr. (Jim Foster (football)), a former executive of the National Football League and the United States Football League. Though not the only variant of indoor football, it is the most widely known, and the one on which most other forms of modern indoor football are at least partially based.

Two leagues have played under the official arena football rules: the original Arena Football League (1987-2008), which played 22 seasons, and arenafootball2 (AF2), which played 10 seasons from 2000 through 2009. The new Arena Football League (Arena Football League (2010)) will also use the arena football rulebook when it begins play in April 2010.