Australia tied their record gold haul at swimming's world championships with one day remaining Saturday, while greats Katie Ledecky and Sarah Sjostrom carved their names deeper into the sport's history.

Australia claimed three more gold medals to take their count to 13 in Fukuoka, tying their best-ever tally from 2001 and 2005.

It secured their place on top of the medal table, meaning they will finish ahead of the United States for the first time since 2001.

Their night's work included a fifth world record this week for Australian swimmers and Kaylee McKeown completing an unprecedented backstroke world title sweep.

Cameron McEvoy, who claimed gold in the men's 50m freestyle, said his teammates' performances had spurred him on.

"It's hard not to tap into that and just go along with the flow," he said.

"It's just good to be a part of that."

American Ledecky won the women's 800m freestyle to become the first swimmer ever to win the same event six times at a world championships.

Sweden's Sjostrom won her fifth in the 50m butterfly, then promptly dived back into the pool and broke her own world record in the 50m freestyle 20 minutes later.

There was also gold for France's Maxime Grousset in the men's 100m butterfly.

Australia's mixed 4x100m freestyle relay team claimed the final title of the day in a world record time, giving Mollie O'Callaghan her fifth gold medal of the week.

"I've had a lot going on this week and I think I've just got to maintain and be as professional as possible," said O'Callaghan.

"Just sticking around with the team and keeping it quite closed has really helped me."

Ledecky claimed her 16th individual world championships gold medal, surpassing fellow American great Michael Phelps.

She cruised home in a time of 8min, 08.87sec to win ahead of China's Li Bingjie on 8:13.31 and Australia's Ariarne Titmus on 8:13.59.

It was Ledecky's second gold of the week, after she retained her 1,500m freestyle title.

Her latest triumph gives her a career haul of 21 world championship golds, extending her record as the most decorated woman in the history of the competition.

Sjostrom won her 20th individual world championships medal by winning the 50m butterfly, tying Phelps for the most ever.

She touched the wall in 24.77sec to win ahead of China's Zhang Yufei on 25.05 and American Gretchen Walsh on 25.46.

The 30-year-old Sjostrom then broke her own 50m freestyle world record, setting a new mark of 23.61sec.

Sjostrom's previous record was 23.67, set at the world championships in Budapest in 2017.

McKeown completed a women's backstroke clean sweep with victory in the 200m on Saturday.

McKeown, who also won the 50m and 100m backstroke, finished in a time of 2min, 03.85sec, ahead of American Regan Smith on 2:04.94 and China's Peng Xuwei on 2:06.74.

McKeown's achievement came one day after China's Qin Haiyang became the first swimmer ever to sweep a stroke at a world championships, winning the men's 50m, 100m and 200m breaststroke events.

Grousset came home in 50.14sec to win the men's 100m butterfly ahead of Canada's Josh Liendo on 50.34 and American Dare Rose on 50.46.

McEvoy won the men's 50m freestyle title, touching the wall in 21.06sec to finish ahead of Jack Alexy of the United States on 21.57 and Britain's defending champion Ben Proud on 21.58.

There was also a world record in the women's 50m breaststroke, with Lithuania's Ruta Meilutyte swimming 29.30sec to tie Italian Benedetta Pilato's mark from 2021.

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