Australian pool queen Emma McKeon said it felt "very surreal" as she clinched a place in the Olympic history books by becoming just the second woman to win seven medals in a single Games.

The 27-year-old finished her Tokyo 2020 campaign with a flourish by winning the 50 metres freestyle in an Olympic record of 23.81 seconds, then playing a key role in Australia's 4x100m medley squad also topping the podium.

She will head home with four golds and three bronzes, and now has the most medals by an Australian in the history of the Olympic Games.

Maria Gorokhovskaya won seven medals for the Soviet Union at the 1952 Olympics in Helsinki, claiming two gold medals and five silver, and now McKeon belongs in such company in the record books.

"I never thought I'd win two gold medals in one session. I’m very happy. It is very surreal," McKeon said.

"I'm very happy with how the meet went. I've been at these kind of meets before where I've been up and down, so I knew what to expect.

"I feel like it has been a bit of a roller coaster getting a gold medal and trying to keep the emotions at bay. It will take a while to sink in because I've been focusing on myself to keep my cool. I'm very proud of myself. I wouldn't be able to do it without all the support around me."

McKeon's parents Ronald and Susie were both international swimmers, as was brother David until his recent retirement.

Setting new Australian medal records was the icing on the cake for the Wollongong native. In a single Olympics, no Australian had previously won as many as seven medals or four golds.

McKeon now has 11 Olympic medals in her career, having won a gold, two silvers and a bronze in Rio five years ago.

The Tokyo haul moves McKeon past Ian Thorpe and Leisel Jones, fellow swimming greats who each won nine medals and were previously top of Australia's all-time list.

"That's also very surreal," McKeon said of the record.

"I look at the athletes who have come before me and been so impressed with what they have done and been inspired by what they have done, but I've never really looked at the stats of medal counts. It is an honour because I know I've worked so hard for it."