During 1993, O'Sullivan established herself as one of the world's top middle-distance runners. By the time the World Championships came around, she was the clear favourite for both the 3000 m and 1500 m. However her hopes in the 3000 m were dashed by the performances of three Chinese athletes who would later in the year go on to smash the world record multiple times. The winner, Qu Yunxia, finished in a championship record of 8:28.71, with Zhang Linli and Zhang Lirong following in second and third respectively. A month later Qu would go on to set a 1500 m world record of 3:50.46. O'Sullivan finished the race 4th in a time of 8:33.8. Six days later she won the silver medal in the 1500 m in a time of 4:03.48, again behind a Chinese athlete. Five days after the championships, at the ISTAF meet in Berlin, O'Sullivan recorded the season's best time over 5000 m of 14:45.92, which moved her to third on the all-time world list. Soon afterwards she closed the year by winning the Grand Prix Final for the 3000 m and finished 2nd in the Mile. She finished the Grand Prix season in 2nd place in the Woman's Overall competition.