The Greek basketball league system is a number of interconnected competitions for professional basketball clubs in Greece. The system has a hierarchical format with a promotion and relegation system between competitions at different levels. There are nine different competition levels in the system. The highest level competitions are the professional and semi professional nationwide competitions, which include the top-tier level Greek Basket League, the second-tier level Greek A2 Basket League, the third-tier level Greek B Basket League, and the fourth-tier level Greek C Basket League. Those competitions are then followed by the regional amateur level competitions, which include: the A1, the A2, the B, the C, and/or the C1, and the C2 categories.
The top-tier level Greek Basket League is organized by the Hellenic Basketball Association (HEBA), while all of the league levels below the top-tier are organized by the Hellenic Basketball Federation (HBF).