Stefanie Maria "Steffi" Graf (German pronunciation: [ˈʃtɛfiː ˈɡʁaːf]; born 14 June 1969) is a German former professional tennis player. She was ranked world No. 1 and won 22 Grand Slam singles titles. Her 22 singles titles put her second on the list of major wins in the female competition since the introduction of the Open Era in 1968 and is third all-time behind Margaret Court (24) and Serena Williams (23). In 1988, she became the only tennis player to achieve the Golden Slam by winning all four Grand Slam singles titles and the Olympic gold medal in the same calendar year. Furthermore, she is the only tennis player to have won each Grand Slam tournament at least four times. 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 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). She and Margaret Court are the only players, male or female, to win three Grand Slam tournaments in a calendar year five times (1988, 1989, 1993, 1995 and 1996). Notable features of Graf's game were her versatility across all playing surfaces, footwork and powerful forehand drive. Graf's athletic ability and aggressive game played from the baseline have been credited with developing the modern style of play that has come to dominate today's game. She won six French Open singles titles (second to Evert), seven Wimbledon singles titles, four Australian Open titles, and five U.S. Open singles titles. She is the only singles player (male or female) to have achieved a Grand Slam since hard court was introduced as a surface at the US Open in 1978. Consequently, Graf's Grand Slam was achieved on grass, clay, and hard court while the previous five Grand Slams were decided on only grass and clay. Graf reached thirteen consecutive major singles finals, from the 1987 French Open through to the 1990 French Open, winning nine of them. She won 5 consecutive major singles tournaments (1988 Australian Open to 1989 Australian Open), and seven out of eight, in two calendar years (1988 Australian Open to 1989 US Open, except 1989 French Open). She reached a total of 31 major singles finals. Graf is regarded by some to be the greatest female tennis player of all time. Navratilova included Graf on her list of great players. In 1999 Billie Jean King said, "Steffi is definitely the greatest women's tennis player of all time." 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. In November 2018, Tennis.com polled its readers to choose the greatest women's tennis player of all time and Graf came in first.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. They have two children – Jaden Gil and Jaz Elle. Graf was inducted into the Tennis Hall of Fame in 2004. Along with countryman Boris Becker, Graf was considered instrumental in popularizing tennis in Germany, where it has remained a highly popular sport ever since.