The National Basketball Association is top men's professional basketball league in the United States and Canada. The league consists of thirty teams; all are located in the United States except for one that is located in Canada.

The league was founded on June 6, 1946 when it was called the Basketball Association of America. It took on the name National Basketball Association in 1949 after a merger with the National Basketball League, a rival league. At this point, the league had seventeen teams located in both small and large cities. The league consolidated its franchises over the next five years to a size of eight.

During the 1950s, the league's franchises in smaller cities moved to large cities. One of these moves was the Fort Wayne Pistons to Detroit in 1957. The 1950s was also the decade in which the color barrier was shattered by African-American players, though the first player to break the color barrier was a Japanese-American named Wataru Misaka who did so in 1947. The 1950s also saw the introduction of the 24-second shot clock in 1954.

The league was dominated by the Boston Celtics in the 1960s, which won the National Basketball Association championship nine of the ten years of the decade, including a championship eight years in a row, a streak that continues to this day. The 1960s also saw the league expand from nine teams to fourteen teams.

During the late 1960s and early 1970s, the National Basketball Association faced the threat of a rival league, the American Basketball Association. The formation of this new league started a bidding war for star players. The National Basketball Association was able to receive one rising star Kareem Abdul-Jabbar; however, some of the National Basketball Association's top players left for the American Basketball Association including Rick Barry who was the league's leading scorer. The American Basketball Association also signed another rising star Julius Erving.

The National Basketball Association continued to expand, however, growing to the size of 18 teams, which lead the merger of the two leagues merger in 1976. Four of the American Basketball Association teams became National Basketball Association teams, which grew the number of teams in the National Basketball Association to 22.

The 1980s was a decade of rivalry between the Los Angeles Lakes and the Boston Celtics. These two teams won the championship eight out of ten times in the decade. These teams were lead by Magic Johnson and Larry Bird, respectively. Five cities also gained basketball franchises during the 1980s.

Michael Jordan brought even more interest into basketball in the 1990s, leading the Chicago Bulls to six championships in eight years during the decade. In 1995, the league gained two more teams, both in Canada. Only one of which, the Toronto Raptors, still remain in Canada.

After the second departure of Michael Jordan, the Western Conference dominated for the next decade, especially the Los Angeles Lakes and the San Antonio Spurs, which combined for nine championships in twelve years.

A season consists of 82 games, followed by a sixteen-team playoff. The playoff culminates in the NBA Finals, a seven-game series between the champions of the Western Conference and the Eastern Conference.