Aaron Finch blasted a national World Cup record 153 as Australia set Sri Lanka 335 for victory at The Oval.
Captain Finch equalled his career-best one-day international innings as Australia dominated the Sri Lanka bowling attack in south London.
Finch's fine and rapid knock eclipsed Ricky Ponting's unbeaten 140 from the 2003 final as Australia's top World Cup innings, as he eyed a fourth win from five matches.
Former skipper Steve Smith hit 73, with Glenn Maxwell's quickfire 46 boosting the final tally to 334 for seven.
Australia would top the World Cup standings with a victory that looked a solid bet at the halfway stage, with Sri Lanka needing a record World Cup run chase to turn the tables.
Ireland's 328 to stun England in 2011 remains the record World Cup chase, so Australia handed Sri Lanka a tall order.
Lasith Malinga produced the ball of the innings to remove Smith, a classic yorker leaving the ex-Australia captain with little option but to watch his stumps be skittled.
Isuru Udana and Dhananjaya De Silva took two wickets apiece, but even some smart spin bowling could not halt Australia for more than isolated pockets.
Two late and sloppy run outs for Alex Carey and Pat Cummins perhaps cost Australia a few runs at the death, but Finch and company were likely happy enough with their work at the crease.
