The National Basketball Association (NBA) is a professional basketball league in North America. The league is composed of 30 teams (29 in the United States and 1 in Canada) and is one of the major professional sports leagues in the United States and Canada. It is the premier men's professional basketball league in the world.

The league was founded in New York City on June 6, 1946, as the Basketball Association of America (BAA). It changed its name to the National Basketball Association on August 3, 1949, after merging with the competing National Basketball League (NBL). In 1976, the NBA and the American Basketball Association (ABA) merged, adding four franchises to the NBA. The NBA's regular season runs from October to April, with each team playing 82 games. The league's playoff tournament extends into June. As of 2020, NBA players are the world's best paid athletes by average annual salary per player.

The NBA is an active member of USA Basketball (USAB), which is recognized by the FIBA (International Basketball Federation) as the national governing body for basketball in the United States. The league's several international as well as individual team offices are directed out of its head offices in Midtown Manhattan, while its NBA Entertainment and NBA TV studios are directed out of offices located in Secaucus, New Jersey. In North America, the NBA is the third wealthiest professional sport league after the National Football League (NFL) and Major League Baseball (MLB) by revenue, and among the top four in the world.

The Boston Celtics and the Los Angeles Lakers are tied with the most NBA championships at 17 each. The Golden State Warriors are the defending league champions, as they defeated the Boston Celtics 4–2 in the 2022 NBA Finals.

The Basketball Association of America was founded in 1946 by owners of the major ice hockey arenas in the Northeastern and Midwestern United States and Canada. On November 1, 1946, in Toronto, Ontario, Canada, the Toronto Huskies hosted the New York Knickerbockers at Maple Leaf Gardens, in a game the NBA now refers to as the first game played in NBA history. The first basket was made by Ossie Schectman of the Knickerbockers. Although there had been earlier attempts at professional basketball leagues, including the American Basketball League and the NBL, the BAA was the first league to attempt to play primarily in large arenas in major cities. During its early years, the quality of play in the BAA was not significantly better than in competing leagues or among leading independent clubs such as the Harlem Globetrotters. For instance, the 1948 ABL finalist Baltimore Bullets moved to the BAA and won that league's 1948 title, and the 1948 NBL champion Minneapolis Lakers won the 1949 BAA title. Prior to the 1948–49 season, however, NBL teams from Fort Wayne, Indianapolis, Minneapolis, and Rochester jumped to the BAA, which established the BAA as the league of choice for collegians looking to turn professional.