Swimming at the 2024 Summer Olympics – Women's 100-metre butterfly

Canada's Maggie Mac Neil was the defending champion going into the event, and six of the finalists (including Mac Neil) from the previous Olympics were returning. Gretchen Walsh set a world record in the event at the 2024 US Olympic Trials, where Torri Huske had swum 0.21 seconds slower to claim the second qualification spot for the US. Huske also won gold at the 2022 World Championships, while China's Zhang Yufei—who also qualified for this event—won gold at the 2023 World Championships. Both SwimSwam and Swimming World predicted that Gretchen Walsh was most likely to win the race. The event was held at Paris La Défense Arena, which was converted to a swimming pool for the swimming events. == Qualification ==

Each National Olympic Committee (NOC) was permitted to enter a maximum of two qualified athletes in each individual event, but only if both of them had attained the Olympic Qualifying Time (OQT). For this event, the OQT was 57.92 seconds. World Aquatics then considered athletes qualifying through universality; NOCs were given one event entry for each gender, which could be used by any athlete regardless of qualification time, providing the spaces had not already been taken by athletes from that nation who had achieved the OQT. Finally, the rest of the spaces were filled by athletes who had met the Olympic Consideration Time (OCT), which was 58.21 for this event. In total, 40 athletes qualified through achieving the OQT, 35 athletes qualified through universality places and two athletes qualified through achieving the OCT. == Heats ==

Four heats (preliminary rounds) took place on 27 July 2024, starting at 11:00. Zhang qualified fastest, swimming 56.50 seconds, while Barbora Seemanová lowered her national record for the Czech Republic by swimming 57.50—0.25 faster than her previous national record from the year prior. Semifinals Two semifinals took place on 27 July, starting at 20:30. Walsh qualified with an Olympic Record of 55.38 seconds, which broke Sarah Sjöström's record from 2016 by 0.10. Huske qualified in second, and Zhang in third. Roos Vanotterdijk broke the Belgian national record by swimming 57.25 seconds. This was 0.22 seconds faster than her previous national record set the month prior but was not enough to qualify. Final The final took place at 20:40 on 28 July. By 25 metres, Zhang Yufei had taken the lead, but by 45 metres Walsh was back in front. At 65 metres (after the second turn and underwater) Walsh was over half a second ahead, having swum a 8.10 50–65 metre split, which was 0.5 seconds faster than anyone else in the race. Over the last 35 metres, Huske came from 0.69 behind to win by 0.04 seconds, pushing Walsh to second and Zhang to third. while David Rieder of Swimming World said "It was a result three years in the making." It was the first time the US had won gold and silver in the event since 1984, and it was Walsh's first Olympic medal. == Notes ==