In a historic final that included three former Olympic record holders and the two previous world record setters, Australian Kaylee McKeown delivered the second fastest time in history, 57.47, to edge out Canada's Kylie Masse and 19-year-old American Regan Smith.
McKeown missed lowering her own world record by .03, settling for the fifth Olympic record set in the event at these very Games.
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Masse got out fastest to the 50-meter, turning ahead of world record pace, but could not hold off the Aussie.
Smith, the Lakeville, Minnesota native, took bronze in 58.05, but was never in touching distance of challenging for gold.
The other American competing in the even, Rhyan White swam well to grab the fourth spot.