Stefanie Maria Graf (born 14 June 1969, in Mannheim, Baden-Württemberg, West Germany) is a former World No. 1 German female tennis player.
In total, Graf won 22 Grand Slam singles titles, second among male and female players only to Margaret Court's 24. In 1988, she became the first and only tennis player (male or female) to achieve the Calendar Year Golden Slam by winning all four Grand Slam singles titles and the Olympic gold medal in the same calendar year.
Graf was ranked World No. 1 by the Women's Tennis Association (WTA) for a record 377 total weeks-the longest period for which any player, male or female, has held the number one ranking since the WTA and the Association of Tennis Professionals began issuing rankings. She also holds the open era record for finishing as the year-end World No. 1 the most times, having done so on eight occasions. She won 107 singles titles, which ranks her third on the WTA's all-time list after Martina Navratilova (167 titles) and Chris Evert (154 titles).
A notable feature of Graf's game was her versatility across all playing surfaces, having won each of the four Grand Slams at least four times, the only player to do so. She won six French Open singles titles (second to Evert) and seven Wimbledon singles titles (third behind Navratilova and Helen Wills Moody). She is the only singles player to have achieved a Calendar Year Grand Slam while playing on all three major types of tennis courts (grass courts, clay courts and hard courts), as the Calendar Year Grand Slams won by other players before her occurred when the Australian and US Opens were still played on grass. Graf reached thirteen consecutive Grand Slam singles finals, from the 1987 French Open through to the 1990 French Open, winning nine of them. She played in 36 Grand Slam singles tournaments from the 1987 French Open, her first Grand Slam win, through the 1999 French Open, her last Grand Slam win, reaching the finals 29 times and winning 22 titles. She reached a total of 31 Grand Slam singles finals, third overall behind Evert (34 finals) and Navratilova (32 finals).
Graf is considered by some to be the greatest female player. Billie Jean King said in 1999, "Steffi is definitely the greatest women's tennis player of all time." Martina Navratilova has included Graf on her list of great players. In December 1999, Graf was named the greatest female tennis player of the 20th century by a panel of experts assembled by the Associated Press. Tennis writer Steve Flink, in his book The Greatest Tennis Matches of the Twentieth Century, named her as the best female player of the 20th century.
Graf retired in 1999 while she was ranked World No. 3. She married former World No. 1 men's tennis player Andre Agassi in October 2001 and they have two children, Jaden Gil and Jaz Elle.