The MLS is the highest level soccer league for the United States and Canada where there are currently 20 teams. The MLS regular season runs from March through October and there are 17 teams based in the United States and three based in Canada. Each team plays 34 games and 12 teams advance to the playoffs where they play for the MLS Cup. The team that has the best record in the regular season is awarded the Supporters' Shield.

The inaugural season for the MLS was in 1993, as the league was formed in order to attract attention to U.S. soccer in order to land the bid for the 1994 World Cup, which was successful. In the first season there were only 10 teams and while the league struggled for the first few years it rebounded in 2002 when there was renewed interest in American soccer after the U.S. advanced to the quarterfinals of the 2002 World Cup. The league continues to increase in popularity, and in 2015 two new teams were added to the league while in 2016 there will be another in Atlanta.

MLS teams also play in other competitions such as the U.S. Open Cup, the Canadian Championship, and the CONCACAF Champions League. The CONCACAF Champions League is the biggest competition of the group and each season up to five clubs from the MLS take part in the tournament, which consists of clubs from the CONCACAF region.

The MLS is the only one of the major leagues around the world that does not have the promotion and relegation format.