Australia smash Olympic record to win women's 4x100 metres freestyle

The quartet of Mollie O'Callaghan, Shayna Jack, Emma McKeon and Meg Harris clocked 3:28.92, just under a second short of Australia's world record, to hold off runners-up United States, while China took the bronze.

The gold added to Australia's elation after Ariarne Titmus defended her 400m title by holding off Summer McIntosh and Katie Ledecky in a contest that had been dubbed Paris' "Race of the century".

Australia have been led by their female sprinters for more than a decade, with their Olympic reign dating back to the 2012 London Games.

On Saturday, they started with Olivia Wunsch and Bronte Campbell in the heats but swapped them out for the unstoppable O'Callaghan and Jack in the final.

O'Callaghan was slow off the blocks and well behind China's leading Yang Junxuan in the opening 50 metres, but once the redhead's furious back-end pace kicked in, there was little doubt Australia would power away.

Jack and McKeon extended Australia's lead before Meg Harris anchored the team home with a sizzling 51.94 second split.

The United States' quartet of Kate Douglass, Gretchen Walsh, Torri Huske and Simone Manuel secured the nation another medal three years after the team's bronze behind Australia and Canada at Tokyo.