The National Lacrosse League (NLL) is a men's professional box lacrosse league in North America. The league is headquartered in Philadelphia, Pennsylvania.

Box lacrosse, also known as boxla, box, or indoor lacrosse, is an indoor version of lacrosse played mostly in North America. The game originated in the 1930s in Canada, where it is more popular than field lacrosse. Lacrosse is Canada's official national summer sport. Box lacrosse is played between two teams of five players and one goalie each, and is traditionally played on an ice hockey rink once the ice has been removed or covered. The playing area is called a box, in contrast to the open playing field of field lacrosse. The object of the game is to use a lacrosse stick to catch, carry, and pass the ball in an effort to score by shooting a solid rubber lacrosse ball into the opponent's goal. The highest level of box lacrosse is the National Lacrosse League.