As England's men wrapped up a 3-0 series win on Sunday, the women secured an impressive five-wicket win in a rain-shortened third one-day international at Hove.
The defeat means England lead the multi-format series by two points with three matches to play - all Twenty20 games.
Australia must win two of the three remaining matches to draw the series and retain the women's Ashes, while only victory in all three would allow them to win the series outright.
Steady overnight rain on England's south coast meant the start of play was delayed by more than three hours, resulting in the game being reduced to 36 overs per side.
Australia looked to have set a tough target after scoring 4-203 on the back of opener Meg Lanning's 64.
But a superb 126-run second-wicket partnership from England's Heather Knight (69) and Sarah Taylor (64) set up the victory for the hosts.
"It's a little bit disappointing to lose an ODI series like that," Australian captain Jodie Fields said.
"I was pretty confident with the 203 we posted on the board and thought we could defend that.
"All we can do now is forget about today, have a rest and switch our focus to the T20s.
"I'm pretty positive. We've had a great 12 months in the T20 part of the game and I think we can turn it around."
Both Knight and Taylor scored at better than a run a ball before being dismissed within two overs of each other to give Australia some hope.
The wickets slowed England's run chase but Lydia Greenway (18) and Natalie Sciver (18 not out) steered England to 5-204 with 16 balls to spare.
Erin Osborne was Australia's best bowler with 3-49.
Earlier, Lanning received good support from dual international Ellyse Perry (45 off 40) and Alex Blackwell (35 off 35), who were both unbeaten at the end of Australia's innings.
The series continues in Chelmsford on Tuesday night.
Top-ranked Australia are chasing their first Ashes win on English soil since 2001.