Squad Leader is a tactical level board wargame originally published by Avalon Hill in 1977. It was designed by Hall of Fame game designer John Hill and focuses on infantry combat in Europe during World War II. One of the most complex wargames of its time, Squad Leader is the natural extension of the trend towards greater realism (and hence complexity) initiated by several earlier games, including Avalon Hill's own PanzerBlitz and Panzer Leader. Those two earlier games were slightly larger in scope, with counters representing platoons and map hexes measuring 250 metres across, compared to Squad Leader's 40 meter hexes and squad sized units. The original Squad Leader was produced in time to debut at Origins '77. (The original print run of 2,500 copies had purple boxes which have become collector's item.) Avalon Hill sold well in excess of 100,000 games of Squad Leader, making it one of the most successful wargames ever made.

In the US military, a squad leader is a non-commissioned officer who leads a squad of typically 9 soldiers (US Army: squad leader and two fireteams of 4 men each) or 13 Marines (US Marine Corps: squad leader and three fireteams of 4 men each) in a rifle squad, or 3 to 8 men in a crew-served weapons squad. In the United States Army the TO&E rank of a rifle squad leader is staff sergeant (E-6, or OR-6) and in the United States Marine Corps the TO rank is sergeant (E-5, or OR-5), though a corporal may also act as a squad leader in the absence of sufficient numbers of sergeants. Squad leaders of crew-served weapons squads range from corporal through staff sergeant, depending upon the branch of service and type of squad.