In 1956, Gibson became the first African-American athlete to win a Grand Slam tournament, the French Championships singles event. She also won the doubles title, partnered with Briton Angela Buxton. Later in the season she won the Wimbledon doubles championship (again with Buxton), the Italian Championships in Rome, the Indian Championships in New Delhi and the Asian championship in Ceylon. She also reached the quarter-finals in singles at Wimbledon and the finals at the US Nationals, losing both to Shirley Fry.