Steffi Graf

The only player in tennis history to achieve the Golden Slam -- winning all four Grand Slams plus Olympic gold in a single calendar year (1988) -- Steffi Graf of Germany won 22 Grand Slam singles titles and held the world number one ranking for 377 weeks, the longest in women's tennis history. Her forehand was the most technically complete shot in women's tennis history, and John McEnroe called her the greatest player of all time, male or female.