Australia's women clinched the 4x100m freestyle relay title with a world record breaking display on Saturday.
Thomas was vital as Australia overcame the United States
Alice Mills, Libby Lenton, Petria Thomas and Jodie Henry clocked three minutes 35.94 seconds to beat the mark of 3:36.00 set by Germany in 2002.
United States took silver in a time of 3:36.39, while Holland made a strong finish to land bronze in 3:37.59.
Britain's quartet of Melanie Marshall, Kathryn Evans, Karen Pickering and Lisa Chapman finished sixth in 3:40.82.
Australia's win was for only the second time they have won the event in
nearly 50 years.
Their previous victory came at the 1956 Melbourne Games in the days of the great Dawn Fraser.
Commonwealth champion Henry stormed past American Jenny Thompson on the anchor leg in the fastest relay split ever of 52.94 seconds, beating the 53.36 of China's ex-Olympic champion Le Jingyi.
Saturday's win also matched the performance of the Australian men's team, who broke the world record on the opening day of the 2000 Games to hand the Americans their first Olympic defeat in the 4x100 freestyle relay.
"I was saying to the girls I can't believe we repeated what the boys achieved in Sydney," Henry said.
"That was so historical and we went and did the exact same thing. It was
Meanwhile, Inge de Bruijn signalled her intentions of defending her title in the women's 100m butterfly by breezing through to the Sunday's final in 57.50.
The Dutch star made the most of a searing start as she held off Australian Petria Thomas in the second semi-final on Saturday.
Thomas, who earlier stormed through the qualifiying with the fastest time of 57.47, finished in 57.93 to earn her place in the final.
Otylia Jedrzejczak, of Poland, was third fastest as she won the first semi-final in 58.10.
Jess Schipper of Australia and Slovakia's Martina Moravcova also made it through to Sunday's showdown, which gets under way at 1757.