The Western Pennsylvania Professional Football Circuit was a loose association of American football clubs that operated from 1890 to approximately 1940. Originally amateur, professionalism was introduced to the circuit in 1892; cost pressures pushed the circuit to semi-professional status from about 1920 through the rest of its existence. Existing in some form for 48 years, it was one of the longest-lived paying football loops to operate outside the auspices of the National Football League.

In the United States and Canada, the term professional football includes the professional forms of American and Canadian gridiron football. In common usage, it refers to former and existing major football leagues in either country. Currently, there are multiple professional football leagues in North America: the two longest-running leagues are the National Football League (NFL) in the U.S, and the Canadian Football League (CFL) in Canada. American football leagues have existed in Europe since the late 1970s, with competitive leagues all over Europe hiring American Imports to strengthen rosters. The Austrian Football League and German Football League top division are known as the best leagues in Europe. The Japan X-League is also a strong league that has a long history since 1971. The NFL has existed continuously since being so named in 1922.