England wrapped up an innings and 83-run victory early on the last day after victory was assured when they had Australia seven wickets down on Thursday`s close.
It was England`s first series victory Down Under since Mike Gatting`s team beat Australia 2-1 in 1986-87.
The tourists posted their highest-ever score in Australia on 644 and dismissed the hapless hosts for 280 and 281.
It was probably England`s most comprehensive performance of the series with Alastair Cook (189), Matt Prior (118) and Ian Bell (115) all claiming centuries in an overpowering first innings lasting 177.5 overs and 758 minutes.
Their bowlers, led by leading series wicket-taker James Anderson, exposed the gulf between the two attacks by dismissing Australia cheaply again.
Steven Smith and Peter Siddle showed some fight with an 86-run eighth-wicket partnership before Siddle holed out to Anderson on the square leg boundary off Graeme Swann for 43 off 65 balls.
Ben Hilfenhaus fell to Anderson caught behind for seven and debutant Michael Beer was the last Australian wicket to fall, bowled by Chris Tremlett for two.
Smith remained unbeaten on 54 in 132 minutes.
England were a potent force during the series, overpowering Australia in huge wins in Adelaide, Melbourne and Sydney, with the Australians winning the third Perth Test. The opening Brisbane Test was drawn.
Alastair Cook was the series topscorer with 766 at 127.66, second only to Wally Hammond`s 905 in 1928-29 for most runs for England in a series in Australia.
Anderson finished the series with 24 wickets, the most by any England bowler since Frank Tyson took 28 in 1954-55 and wicketkeeper Matt Prior took 23 catches in the series.
England were the last team to beat Australia at the SCG in 2003 when Andy Caddick claimed 7-94 after Michael Vaughan had amassed 183 in the second innings to pull off a massive 225-run triumph.
England have now won 22 times in Sydney in 54 Tests.
The Ashes humiliation was Australia`s sixth defeat in their last eight Tests and comes at a time of major upheaval in all facets of the Australian game.
Michael Clarke stood in for injured skipper Ricky Ponting for the Sydney Test and came away with a similar result.
Only Mike Hussey with 570 runs and two centuries at 63.33 emerged with his reputation intact as Ponting (113 runs at 16) and Clarke (193 at 21.44) failed miserably with the bat.
Australia`s leading contemporary wicket-taker Mitchell Johnson also had an under-performing series -- taking 15 wickets at an expensive 36.93.
Australia`s diabolical performance is expected to lead to an inquest with the administrators, selectors, coaches and players under scrutiny amid widespread public disenchantment.