John Albert Kramer was an American tennis

Tennis

Tennis is a sport usually played between two players or between two teams of two players each . Each player uses a racket that is strung to strike a hollow rubber ball covered with felt over a net into the opponent's court. Tennis is an Olympic sport and is played at all levels of society at all...

 player of the 1940s. A World Number 1 player for a number of years, he is a possible candidate for the title of the greatest tennis player of all time. He was considered the father

Father

A father, Pop, Dad, or Papa, is defined as a male parent of any type of offspring. The adjective "paternal" refers to father, parallel to "maternal" for mother...

 and the leading promoter of the professional tennis tours. He was a relentless advocate for the establishment of Open Tennis between amateur and professional players.