Gilchrist slammed 12 fours and four sixes to reach his hundred off just 57 balls. He finished unbeaten on 102 as the world champions amassed a daunting total of 527 for five declared.
Set 557 for victory to keep the series alive, England's hopes of a miracle plummeted when opener Andrew Strauss departed for a fourth-ball duck before they limped to the close on 19 for one.
Michael Clarke (135 not out) and Mike Hussey (103) also made hundreds after Matthew Hayden (92) and Ricky Ponting (75) narrowly missed out, Australia's batsmen going on the rampage against a dispirited England bowling attack.
England beat Australia 2-1 in an epic series at home last year to win the Ashes for the first time in 16 years but face the prospect of handing them back after just 15 months - the shortest reign since the Ashes were first contested in 1882.
Gilchrist set a series of records as he chalked up his 17th Test hundred in spectacular fashion despite arriving at the crease after the tea break.
The Australian wicketkeeper equalled Graham Thorpe's record for the fastest Ashes fifty when he reached the milestone off just 40 balls.
He also set a record for the most runs off a single six-ball Ashes over when he plundered 24 off spinner Monty Panesar and brought up his hundred in just one more ball than Viv Richard's world record of 56, set against England at St. Johns in 1985-86.
Gilchrist's display overshadowed another fine performance by Clarke and Hussey. Clarke's 135 came off just 164 balls and featured 17 fours and a six and Hussey became the first Australian to score five successive half-centuries in an Ashes series before completing his first ton of the series.
England made a bright start when they picked up the prized wickets of Ponting and Hayden before lunch but missed their chance to restrict Australia to a smaller total with poor fielding.
The left-handed Hussey survived a chance on 48 when he skied a hook off Steve Harmison that fell between three English fielders and he had another let-off on 78 when he was dropped in the slips by Strauss.
England wicketkeeper Geraint Jones also missed a stumping off Clarke before the Australian had reached double-figures.
Australia 244 and 527 for 5 decl (Michael Clarke 135 n o, Gilchrist 102 n o, Hussey 103, Hayden 92, Ponting 75; Panesar 3 for 145) Vs England 215 and 19 for 1 (Bell 9 n o, Cook 7 n o; Brett Lee 1 for 5)