Stefanie Maria Graf (born June 14, 1969, in Mannheim, Baden-Württemberg, West Germany) is a former World No. 1 female tennis player from Germany.

Graf won 22 Grand Slam singles titles, second among male and female players only to Margaret Court's 24. She is the only player to have won all four Grand Slam singles tournaments (Wimbledon, the US Open, the French Open and the Australian Open) at least four times each. In 1988, Graf 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 of any player, male or female, 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. 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