Bairstow came to the crease with England in a familiar state of turmoil at 36-4, but defied a 90mph blow to the right thumb as he counter-attacked his way to 103 not out at the SCG.
The Yorkshireman averaged 21.32 in the 19 games since he last reached three figures, against Sri Lanka in November, 2018, but answered longstanding questions over his red-ball future with a gutsy counter-attack that will live long in the memory.
Whether or not it is enough to save England from going 4-0 down remains to be seen, but it will surely save Bairstow from being involved in the round of ritual blood-letting that looks likely to take place at the end of a grim tour.
Bairstow had a nervy wait to reach his seventh Test century at the end of the day, carving the fourth ball of the final over for four to kick off a passionate celebration. That left England 258-7, still 158 behind but having finally shown some steel worthy of the old rivalry.
Coming in at the depths of yet another top-order collapse Bairstow shared a restorative stand of 128 with Ben Stokes, who bludgeoned his way to 66 after an outrageous slice of luck, and ended with eight fours and three sixes.
Stokes had offered no shot to an 83mph delivery from fellow all-rounder Cameron Green with 16 to his name and saw the ball connect healthily with his off stump. Ordinarily that would be more than enough to send a batter back to the pavilion with his tail between his legs, but to Australia’s amazement - and Stokes’s amusement - the bail stubbornly refused to budge.
Stokes’s lively response was cut short when he was trapped lbw by Nathan Lyon and when Bairstow saw his thumb jammed back viciously by a Pat Cummins bouncer off the very next ball, his knock looked to be over at 61.
He required lengthy treatment from the physio and looked to be heading for an enforced retirement, but he refused to give up his spot. Instead he continued to swing from the hip en route to England’s first century of the series.
Bairstow was not the only England batter to wear some bruises on a day that saw fiendishly unpredictable bounce from a bowling attack with the perfect skills to exploit it.
Bandages are likely to be in short supply in the away dressing room as a barrage of body blows and finger-busting shots rained down on the walking wounded tourists.
The morning’s play was heavily delayed and shortened by rain, but there was still more than enough time for Australia to tie England’s top four in knots.
Haseeb Hameed was first to go as he continued a desperate tour that could send his international career back into hibernation. Having been dropped off his third ball of the day, a loose nick off Mitchell Starc that wicketkeeper Alex Carey fumbled, he was cleaned up for six playing a ragged drive at the same bowler.
Averaging a shade over 10 for the series, his prospects of making the finale in Hobart look slim. Zak Crawley made a streaky 18 before suffering the same fate, swinging down the ground at Scott Boland and losing his off stump.
England did not know it at the time but they were at the start of an absurdly one-sided period that saw a hypnotic sequence of 70 consecutive dot balls either side of lunch.
During that long scoreless streak, they lost three wickets as Boland got Joe Root flaying to slip for a duck and Dawid Malan flicked Green to the catcher at leg-slip.
Stokes ended the drought with thick edge for one and, as soon as he had his bizarre let-off, launched the fightback. He backed his ball-striking, at one stage slamming Starc for the three fours in a row and aggravating his side strain in the process.
Bairstow followed suit, going after Lyon with a wonderful array of sweeps, cuts and drives. Stokes was unable to go big, sitting deep and beaten by the spinner’s arm ball, but Bairstow dug in after getting hurt.
Twice he slog-swept Lyon into the stands, then swatted Green for more of the same. He almost ran out of time to reach his hundred but timed his charge perfectly, slashing Cummins to third man.
Jack Leach was on hand to share the moment, Jos Buttler having bagged an eight-ball duck before a thrilling cameo of 39 from Mark Wood. But this was Bairstow’s day and he led the teams off to well-earned acclaim.