Major professional sports leagues in the United States and Canada typically consist of four major leagues: Major League Baseball (MLB), the National Basketball Association (NBA), the National Football League (NFL), and the National Hockey League (NHL). Other notable leagues include Major League Soccer (MLS) and the Canadian Football League (CFL).

These major leagues, along with the English Premier League, are considered the wealthiest professional club competitions in their respective sports and are among the top five sports leagues in the world in terms of revenue.

Each of the Big Four leagues, as well as MLS and the CFL, have a significant fan base, with average attendance per game exceeding 15,000 as of 2023. The NFL has the largest stadiums, with capacities ranging from just under 60,000 to almost 100,000 spectators. MLB ballparks generally hold between 30,000 and 50,000 fans. MLS and CFL venues have a wider range of capacities, from about 20,000 to about 60,000. The NHL and NBA, which are indoor leagues, typically play in arenas with capacities of 18,000 to 20,000 seats.

The Big Four leagues currently have 30 to 32 teams each, primarily located in the most populous metropolitan areas of the United States and Canada. Unlike sports leagues in other regions that utilize promotion and relegation systems, North American sports leagues are closed leagues, meaning the teams remain the same from season to season. Expansion of these leagues usually occurs through the addition of new teams, although mergers with competing leagues have also taken place.

Baseball, American football, and ice hockey have had professional leagues for over 100 years, while basketball’s first professional league was formed in the 1920s. Soccer (or association football) was professionalized in 1894, with past American leagues including the American Soccer League (ASL) and the original North American Soccer League (NASL). Major League Soccer (MLS) was established in 1996.

Each of the Big Four leagues has its own rich history. Major League Baseball, founded in 1876, consists of the National League and the American League and is considered the highest level of play worldwide. The National Basketball Association, founded in 1946 as the Basketball Association of America, is globally recognized as the top basketball league. The National Football League, established in 1920, is the premier professional American football league. The National Hockey League, founded in 1917, is widely regarded as the top professional ice hockey league.

These major leagues, along with MLS and the CFL, have become integral parts of the sports landscape in the United States and Canada. They attract large audiences, generate significant revenue, and showcase world-class talent.