Grand Slam (tennis) tennis ball, Martina Navratilova finally did it." Although the ITF recognizes what is now unofficially known as the "non-calendar year Grand Slam" on its Roll of Honour, no subsequent player to win four or more majors in a row—Steffi Graf, Serena Williams, or Novak Djokovic—has received bonus prize money. Combining "the" Grand Slam and non-calendar year Grand Slam, the total number of times that players achieved the feat (of being the reigning champion in all four majors) expands to 18. Three women have won four or more consecutive major titles since 1970, with Navratilova taking six in a row in
Grand Slam (tennis) feat twice in men's singles; Margaret Court accomplished the feat three times, in two different disciplines – once in women's singles and twice in mixed doubles; and Esther Vergeer completed a grand slam twice in Women's wheelchair doubles. The four Junior disciplines, boys' and girls' singles and doubles, provide limited opportunities to achieve a Grand Slam. Players are only eligible from age 13 to 18, with 18-year-olds likely to hold a physical advantage. Only Stefan Edberg has completed the Grand Slam in a Junior discipline. In 1982, the International Tennis Federation (ITF) began offering a $1 million bonus to any