This article details the list of men's singles Grand Slam tournaments tennis champions. Some major changes have taken place in history and have affected the number of titles that have been won by various players. These have included the opening of the French national championships to international players in 1925, the elimination of the challenge round in 1922, and the admission of professional players in 1968 (the start of the Open era). From 1913 to 1923 there were three official championships recognized by the ILTF: * U.S. National Championships, held in New York on grass.