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).