John Albert Jack Kramer (August 1, 1921 – September 12, 2009) was an American tennis player of the 1940s and 1950s. A World No. 1 player for a number of years, and one of the most important people in the establishment of modern mens Open-era tennis, he was the leading promoter of professional tennis tours in the 1950s and 1960s. He was a relentless advocate for the establishment of Open Tennis between amateur and professional players. An International Tennis Federation (ITF) proposal to introduce Open tennis lost by five votes in 1960, but became a reality in 1968. In 1970, he created the Mens Grand Prix points system. In 1972, he helped found the Association of Tennis Professionals (ATP) with Donald Dell and Cliff Drysdale, and was the first Executive Director. He was unpaid at his request. In that role, he was the leader of an ATP boycott of Wimbledon in 1973, for the banning of Nikola Pili? from the tournament.
Tall and slim, he was the first world-class player to play the Big Game, a consistent serve-and-volley game, in which he came to the net behind all of his serves, including the second serve. He was particularly known for his powerful serve and forehand, as well as his ability to play percentage tennis, which he learned from Cliff Roche, a retired railroad engineer, at the Los Angeles Tennis Club (LATC). This strategy maximized his efforts on certain points and in certain games during the course of a match to increase his chances of winning. The key was to hold serve at all costs, which was one of many things that made Kramer one of the greatest players of all time.