Japan B League 1

The Japan Basketball Association was formed in 1930 and has operated Japan's top basketball leagues under various names since 1967. Throughout the history of the association, teams have been affiliated with large corporations and players have been employed by their respective owner company rather than competing as professional basketball players. In the early 1990s soccer in Japan moved away from a similar corporate structure and launched the J.League in 1993. The JBA commenced investigating the professionalization of basketball in the same year, and in 1997 lifted the ban on professional players. Despite this, the structure of the Japan Super League remained amateur in nature, with most teams remaining under the control of a corporate sponsor/owner.

In 2005 a rival bj league was launched in competition with the Super League, based on an American franchise system of professional teams. In response, the JBA re-launched the Super League as the Japan Basketball League (JBL) in 2007, but there was still a mixture of professional and corporate teams in the competition. The JBL was again rebranded as the National Basketball League in 2013. Since the establishment of the bj league in 2005, both competitions rapidly expanded the number of teams, with 45 teams participating between the two competitions in 2015.

FIBA, the international governing body for basketball, grew concerned with the division and disorganization of the sport within the country. After the JBA failed to comply with deadlines to commence reorganizing the domestic leagues, FIBA suspended Japan from international competitions in November 2014. A task force to investigate the reformation of the domestic leagues was formed and Saburō Kawabuchi was appointed co-chairman. In May 2015, upon FIBA's recommendation, Kawabuchi was appointed as president of the JBA. The merger of the two competing leagues into the B.League was announced in June 2015 and the international suspension was lifted by FIBA in August. Telecommunications company Softbank were named as the league's top sponsor for the inaugural season in March 2016.

The 2016–17 season commenced with an inaugural match between four-time JBL/NBL champions Alvark Tokyo, who finished on top of the NBL ladder in 2015–16, and four-time bj-league champions Ryukyu Golden Kings, who won the 2015–16 bj-league championship, at Yoyogi National Gymnasium on 22 September 2016. A full round of games involving all other teams commenced on September 24.

Since the 2021–22 season, the winners and runners-up of each season qualify for the East Asia Super League.