Meg Lanning struck the highest individual score in a Women's T20 international as Australia defeated England by 93 runs at a sold-out Chelmsford to clinch the Women's Ashes outright.
Having retained the trophy in Taunton as the teams drew the only Test match of the multi-format series, the Southern Stars extended their lead to 10-2 points as they restricted the hosts to 133-9 in their chase of 227.
Lanning pummeled a career-best unbeaten 133 off just 63 balls in an exceptional innings that included 17 fours and a mammoth seven maximums, as she surpassed her own record high score of 126.
The Australian skipper shared a century stand with Beth Mooney (54) as the tourists also hit their highest team T20I total of 226-3.
England capitulated in the face of their steep total, losing openers Danni Wyatt and Amy Jones for ducks and seeing captain Heather Knight run out for three as they slipped to 22-4.
Nat Sciver (28), Lauren Winfield (33) and Katherine Brunt (29no) provided some entertainment but they could not stop England slumping to their heaviest T20I defeat against Australia.
It was a first-ever loss for the hosts at the ground previously referred to as 'Fortress Chelsmford' having won all of the 14 prior matches in Essex.
Lanning lights up Chelmsford
4,500 spectators packed into the County Ground in expectation of being entertained by Heather Knight's side in a place that has offered much delight and comfort for the home side over the last decade.
After being put in to bat, the dangerous Alyssa Healy was well caught on the circle off Kate Cross in the opening over but it proved to be a false dawn for England.
Lanning and Mooney struck 12 boundaries between them during the powerplay to propel Australia to 62-1 after the opening six overs and they continued to find the ropes with ease even once the fielding restrictions had been relaxed.
The Australian skipper brought up her half-century off only 24 balls and Mooney followed suit reaching her milestone off from 28 balls.
Having reached 106-1 at the half-way stage of their innings, Lanning tore into Laura Marsh - pummeling the spinner's third over for a pair of sixes - the first flying into the hands of a spectator in leg side, the second smashing into the Sky Pod in the mid-wicket region.
Although Ecclestone bowled Mooney for 54 to bring an end to the 134-run second-wicket stand, Lanning remained laser-focused on reaching three figures as she made the most of a sub-optimal fielding performance from England.
Beaumont was guilty of shelling an easy catch at point to dismiss the Southern Stars' leader on 85 and Lanning used her slice of luck to bring up a classy century by a huge six off the second ball of Anya Shrubsole's third over.
Refusing to take her foot off the peddle, she finished the 117th over in style, launching the last ball of the over down the ground for an enormous six having hit back-to-back fours off the previous two deliveries.
A tidy cameo of 27 off 14 balls from Ashleigh Gardner propelled Australia past 200 and Lanning surpassed her 127 against Ireland by smiting a full toss from Brunt for six as she finished the innings in emphatic method.
Batting collapse costs England once more
In November 2017, Wyatt struck her maiden century to help England chase down 179 and earn her side an 8-8 points draw in the previous Women's Ashes.
Faced with the same task in Essex, with the hosts needing to win every T20I to earn another 8-8 points draw, Wyatt lasted just four balls before her attempted slog over extra cover saw an outside edge fly into the diving hands of Gardner at third man as Ellyse Perry picked a wicket in the first over of the chase.
Megan Schutt followed suit, ending her maiden over with the scalp of Jones - as the England opener chipped the No.1 ranked T20I bowler to mid-on.
The collapse was in full flow as Perry's second over saw Beaumont caught behind for eight and Sciver called for a quick single, selling Knight well short at the striker's end with Mooney's pinpoint throw accounting for the England captain.
Sciver's counter-attack was ended when she lobbed a simple return-catch to Sophie Molineux and Winfield then departed as she sliced a slower delivery from Schutt to short third man.
England were never able to recover from the early damage and though Marsh (25) managed to strike a couple of late sixes, it was far too little to stop Australia motoring on.
Watch the second T20I in the multi-format Women's Ashes live on Sky Sports Cricket from 1.30pm on Sunday.