Major League Lacrosse (MLL) was a men's field lacrosse league in the United States. The league's inaugural season was in 2001. Teams played anywhere from ten to 16 games in a summertime regular season. This was followed by a four-team playoff for the championship trophy, the Steinfeld Trophy, named after founder Jake Steinfeld. League attendance peaked at 6,417 in 2011 and the 2019 average was 4,587.

Field lacrosse is a full contact outdoor sport played with two opposing teams of ten players each. The sport originated among Native Americans, and the modern rules of field lacrosse were initially codified by Canadian William George Beers in 1867. Field lacrosse is one of three major versions of lacrosse played internationally. The rules of men's lacrosse differ significantly from women's field lacrosse. The two are often considered to be different sports with a common root. An outdoor six-a-side version, lacrosse sixes, was established in 2021 and features six players per team, reduced field size, and shorter duration to be conducive for daily tournament play. Another version, indoor box lacrosse, is also played under different rules.