Major League Soccer (MLS) is a professional soccer league, sanctioned by U.S. Soccer, that represents the sport's highest level in both the United States and Canada. MLS constitutes one of the major professional sports leagues of the United States and Canada. The league is composed of 20 teams—17 in the U.S. and 3 in Canada. The MLS regular season runs from March to October, with each team playing 34 games; the team with the best record is awarded the Supporters' Shield. The post season includes twelve teams competing in the MLS Cup Playoffs through November and December, culminating in the championship game, the MLS Cup. MLS teams also play in other domestic competitions against teams from other divisions in the U.S. Open Cup and in the Canadian Championship. MLS teams also compete against continental rivals in the CONCACAF Champions League.