Stefanie Maria Graf (born June 14, 1969, in Mannheim, West Germany) is a former World No. 1 ranked female tennis player from Germany. Graf is widely considered to be one of the greatest female tennis players in history. Graf won 22 Grand Slam singles titles, second among male and female players only to Margaret Court's 24. She also won 107 singles titles, which ranks her third on the list of most singles titles won during the open era, behind Martina Navratilova (167 titles) and Chris Evert (154 titles). 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 1988, Graf won the Olympic gold medal in singles and all four Grand Slam singles titles that year, becoming the first and only player to win the "Golden Slam."

She was ranked the Women's Tennis Association's No. 1 player for a record 377 total weeks the longest of any player, male or female, since rankings began and is the only player to have won all four Grand Slam singles tournaments (Wimbledon, the U.S. Open, the French Open, and the Australian Open) at least four times each. Graf also holds the record (eight) for most years as year end number one.

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 across all three types of tennis courts, as the other Calendar Year Grand Slams won by other players occurred when the Australian and U.S. Opens were still played on grass. Graf reached thirteen consecutive Grand Slam singles finals, from the French Open in 1987 through the French Open in 1990, winning nine of them. She played in 36 Grand Slam singles tournaments from the 1987 French Open through the 1996 U.S. Open, reaching the finals 29 times and winning 21 titles. Her 22nd and last Grand Slam title was the French Open in 1999. She reached 31 Grand Slam singles finals, third overall behind Evert (34 finals) and Navratilova (32 finals).

Graf retired in 1999, giving her the distinction of being the highest ranked player ever to retire, at No. 3 in the world. She is married to the former World No. 1 men's tennis player Andre Agassi.