Stefanie Maria "Steffi" Graf is a German former professional tennis player. She was ranked world No. 1 and won 22 Grand Slam singles titles. Her 22 singles titles put her second on the list of major wins in the female competition since the introduction of the Open Era in 1968 and is third all-time behind Margaret Court and Serena Williams. In 1988, she became the only tennis player to achieve the Golden Slam by winning all four Grand Slam singles titles and the Olympic gold medal in the same calendar year. Furthermore, she is the only tennis player to have won each Grand Slam tournament at least four times.