Martina Hingis (born September 30, 1980, Košice, Czechoslovakia [now in Slovakia]) is a Swiss professional tennis player who became the youngest person in the “open” era to win a Grand Slam singles title and the youngest to be ranked world number one. In her relatively short, injury-plagued career, she won five Grand Slam singles titles—the Australian Open (1997, 1998, 1999), Wimbledon (1997), and the United States Open (1997).