Virginia Slims World Championship Series

The Virginia Slims World Championship Series (its sponsored name) or WTA World Championship Series (its tour name) was the women's top tier tennis tour administered by the Women's Tennis Association that was first founded in 1970 as the Virginia Slims Series of events that were then part of ILTF World Circuit. It eventually became the basis for the later WTA Tour. The players, dubbed the Original 9, rebelled against the United States Lawn Tennis Association (USLTA) because of the wide inequality between the amount of prize money paid to male tennis players and to female tennis players. In 1971 it was rebranded as the Virginia Slims Circuit until 1978 and was a rival tour to the ILTF Women's International Grand Prix until 1976. In 1979 it was branded as the Avon Championship Circuit until 1981. In 1982 it was merged with the Toyota International Series as a single women's tennis tour and rebranded under its last title name until 1989. In 1990 it was succeeded by the WTA World Tour.