Emma McKeon has claimed her historic seventh swimming medal at the Tokyo Olympics with Australia's victory in the women's 4x100-metre medley relay.

The 27-year-old from Brisbane becomes the first female swimmer to win seven medals at a single games. The only men to do it are Michael Phelps, Mark Spitz and Matt Biondi.

Capping a brilliant performance by the entire Aussie women's team, McKeon followed her victory in the 50-freestyle earlier in the session to take the butterfly leg on the relay. Cate Campbell closed strong on the freestyle, touching in an Olympic record of 3 minutes, 51.60 seconds to edge the two-time defending champion Americans.

Canada won the bronze in 3:52.60, giving Penny Oleksiak her own piece of history as the only Canadian to win seven medals in the Olympics. She won three in Tokyo to go with her four she won in Rio five years ago.

Kaylee McKeown and Chelsea Hodges started things off for the winning Australian team.

Abbey Weitzeil touched in 3:51.73 to give the United States a silver. She anchored a team that also included teenagers Regan Smith, Lydia Jacoby and Torri Huske.

American Caeleb Dressel has won his fifth gold medal of the Tokyo Games, finishing off one of the great performances in Olympic history.

Dressel swam the butterfly leg as the Americans set a world record in the 4x100m medley relay with a time of three minutes, 26.78 seconds. That eclipses the mark of 3:27.28 they set at the 2009 Rome world championships in rubberized suits.

Ryan Murphy, Michael Andrew and Zach Apple joined Dressel on the winning team. That ensured the Americans closed out the swimming competition with another gold in a race they've never lost at the Olympics.

Earlier in the session, Dressel won the 50m freestyle for his third individual title of the games. He also won two golds on the relays.