Kaylee McKeown is the first Australian to win four individual Olympic gold medals after triumphing in the women's 200m backstroke.
McKeown is also the first swimmer to successfully defend 100m and 200m backstroke titles in Olympic history.
The 23-year-old has collected Australia's 10th gold medal in Paris.
Compatriot Cameron McEvoy won the men's 50m freestyle gold just 10 minutes before McKeown saluted on Friday night.
McKeown now has five golds in her Olympic career, with a women's 4x100m medley victory at the Tokyo Games three years ago also in her collection.
"Not in a million years ... I couldn't ask for much more," she said of her medal haul.
Fellow swimmer Emma McKeon holds the Australian record for most Olympic golds - she has won six, with four coming in relays.
McKeown kept her 200m backstroke title in stunning style, clocking an Olympic record time of two minutes 03.73 seconds, some 0.59 seconds shy of her world record set last year in Sydney.
McKeown was third after at the midpoint and second at the final turn before powering to victory ahead of American Regan Smith (2:04.26) and Canada's Kylie Masse (2:05.57).
McKeown defended her 100m backstroke crown on Tuesday night and her victory over the longer distance gives Australia's swim team a seventh gold medal in Paris.
Other Dolphins winners in the French capital are Ariarne Titmus (women's 400m freestyle), the women's 4x100m freestyle relay team, Mollie O'Callaghan (women's 200m freestyle), the women's 4x200m freestyle team and McEvoy.