Canada's defending World champion Maggie Mac Neil pulled away from a tight field to win her nation's first Olympic title in the event.

Swimming out in lane 7, Mac Neil touched seventh at the 50 m mark but used a blistering underwater off the turn to catapult herself near the front and win gold in an Americas record of 55.59.

Australia's Emma McKeon reset her Oceanian record from the heats to win bronze in 55.72, edging out the U.S.' Torri Huske (55.73) by one hundredth of a second.

Sweden's defending champion Sarah Sjöström, coming off elbow surgery in February, produced a valiant effort to place seventh in 56.91 - her slowest time throughout the rounds.

Up to one swimmer per NOC meeting that time is eligible for selection, allocated by world ranking until the maximum quota for all swimming events is reached.