Jason Roy hit England's highest ODI score as England completed a record chase at the MCG.
Roy blasted 180 from 151, surpassing Alex Hales' previous record by nine runs, as England comfortably overhauled Australia's 304/8.
Joe Root was unbeaten on 91 to see England to a win in the opening game of the series.
Team News and Toss
England captain Eoin Morgan declared before play that his team would be built around a strong batting line-up, and the tourists were able to name fit-again Joe Root in the side, with Sam Billings and Tom Curran missing out from the 12-man side that played in the warm-up match against a Cricket Australia XI in Sydney.
Before play, England's all-time leading Test wicket-taker James Anderson presented vice-captain Jos Buttler with his 100th ODI cap. Australia, meanwhile, handed a debut to 31-year-old seamer Andrew Tye.
England won the toss and Morgan chose to bowl first.
Australia set England record run chase
Australia opener Aaron Finch scored his ninth ODI century as England were set 305 to win - a record run-chase in an ODI at the MCG.
Finch was eventually dismissed by Moeen Ali after anchoring Australia's innings with 107 from 119 balls.
Mark Wood bowled with pace and venom - his fastest ball was clocked at 92.7mph - and removed the hosts' dangerman David Warner for just two runs with a rapid short ball.
Australia captain Steve Smith, a thorn in England's side all winter, made only 23 before being caught behind by Buttler off Adil Rashid, one of three wickets for the leg spinner.
Mitch Marsh supported Finch with a solid 50 from 68 balls while Marcus Stoinis' innings of 60 from 40 balls allowed Australia to creep past 300 to finish on 304/8.
England cruise to historic victory
A masterclass from Roy inspired England to victory by five wickets with seven balls to spare.
Roy flew out of the traps along with opening partner Jonny Bairstow, who edged behind for 14 before new batsman Alex Hales only made four.
That brought Root to the crease and England's Test captain consolidated with Roy as the Three Lions settled down in the middle overs in the knowledge they were well ahead of the run rate.
The pair ended with a partnership of 221 - a record third-wicket stand for England in ODIs - while Roy surpassed team-mate Alex Hales to score the Three Lions' highest ever individual total in the format.
"I'm struggling for words. It's an incredible feeling."
Stat of the Day
- In 148 ODIs at the MCG, this is the first time a side has scored more than 300 batting second at the MCG.
- Jason Roy's 180 is England's highest score in an ODI.
- It is also the highest score in an ODI at the MCG.
- Roy's 221-run partnership with Joe Root was England's highest for the third wicket.
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