Stefanie Maria "Steffi" Graf (born 14 June 1969, in Mannheim, Baden-Württemberg, West Germany) is a former World No. 1 German tennis player.
In total, Graf won 22 Grand Slam singles titles, second among male and female players only to Margaret Court's 24. Her 22 singles titles mark the record for most Grand Slam wins by a tennis player (male or female) since introduction of the Open Era in 1968. 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 (157 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, and she is best known for her great footwork and for her powerful forehand drive. Graf 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 (male or female) to have achieved a Calendar Year Grand Slam while playing on four different types of tennis courts (Rebound Ace, grass, clay and DecoTurf), 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, 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 regarded by some to be the greatest female tennis player of all time. Billie Jean King said in 1999, "Steffi is definitely the greatest women's tennis player of all time," although on other occasions King has said that Martina Navratilova holds that title. Navratilova herself 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. In March 2012, Tennis Channel picked Graf as the greatest female tennis player ever in their list of 100 greatest tennis players of all time.
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. The couple have two children – Jaden Gil and Jaz Elle. Graf was inducted into the Tennis Hall of Fame in 2004.