Steffi Graf completed the Golden Slam in 1988.
Graf won all four women's singles major championships that year: the Australian Open, French Open, Wimbledon and US Open. She then added the Olympic women's singles gold medal at the Seoul Games, completing the rare combination known as a Golden Slam. The Olympic final took place on 1 October 1988, when Graf defeated Gabriela Sabatini 6–3, 6–3.
Her 1988 season was extraordinary because she won the Grand Slam before claiming Olympic gold. She defeated Chris Evert in the Australian Open final, Natasha Zvereva in the French Open final, Martina Navratilova at Wimbledon and Gabriela Sabatini at the US Open. The French Open final lasted only 34 minutes and ended 6–0, 6–0.
A Golden Slam is not simply winning all four majors during a career. It means winning the four majors and Olympic singles gold in the same calendar year. Graf remains the only singles player to complete that achievement, and 1988 was the first year tennis returned as a full Olympic medal sport since 1924.