The 1975 World Championship Tennis circuit was one of the two rival professional male tennis circuits of 1975. It was organized by World Championship Tennis (WCT). The 1975 circuit divided the players in three groups, Red, Blue and Green who played 24 tournaments in 12 countries. The first tournament, U.S. Professional Indoor Championships, was a combined event as was the season's final which was played in Dallas by the eight best performers and was won by American Arthur Ashe who defeated Björn Borg from Sweden in four sets.

The 1974 World Championship Tennis (WCT) circuit was one of the two rival professional male tennis circuits of 1974, the other being the Grand Prix circuit. It was organized by World Championship Tennis (WCT). It was the fourth edition of the WCT circuit and a total of 84 players participated. All players took part in the opening U.S. Pro Indoor tournament in Philadelphia and afterwards were divided into three groups of 28 players, with each group playing eight further tournaments.