The National League of Professional Baseball Clubs, known simply as the National League (NL), is the older of two leagues constituting Major League Baseball (MLB) in the United States and Canada, and the world's oldest extant professional team sports league. Founded on February 2, 1876, to replace the National Association of Professional Base Ball Players (NAPBBP) of 1871–1875, the NL is sometimes called the Senior Circuit, in contrast to MLB's other league, the American League, which was founded 25 years later and is called the "Junior Circuit". Both leagues currently have 15 teams.

Major League Baseball (MLB) is a professional baseball league and the highest level of organized baseball in the United States and Canada. One of the big four major leagues, MLB comprises 30 teams, divided equally between the National League (NL) and the American League (AL), with 29 in the United States and 1 in Canada. Formed in 1876 and 1901, respectively, the NL and AL cemented their cooperation with the National Agreement in 1903, making MLB the oldest major professional sports league in the world. They remained legally separate entities until 2000, when they merged into a single organization led by the Commissioner of Baseball. MLB is headquartered in Midtown Manhattan.