Steffi Graf plays tennis.
Steffi Graf . In 1988 , she became the first and only tennis player ( male or female ) to achieve the Golden Slam by winning all four Grand Slam singles titles and the Olympic gold medal in the same calendar year . Graf is regarded by some to be the greatest female 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 .