Full-time score from Gigg Lane
A stunning three goal blast from Shaun Williams (pen), Calum Butcher and Aiden O'Brien in the last 20 minutes completed a memorable fightback as Millwall turned a 2-0 deficit into a 3-2 victory at Bury.
Bury were within touching distance of bringing an horrendous run of nine consecutive League defeats to an end when a second-half brace from James Vaughan gave the struggling Shakers a two-goal cushion with 67 minutes on the clock.
But no sooner had Vaughan added his second goal, Niall Maher inexplicably handled on the line to keep out Fred Onyedinma's shot and was shown a straight red card. Midfielder Williams made no mistake from the resulting penalty and The Lions took full advantage of their numerical advantage as sub Butcher headed home the equaliser before fellow sub O'Brien sparked wild celebrations with a dramatic winner in the second minute of injury time in a stunning turnaround.
On a freezing cold afternoon, a hardy crowd of 3,022 - boosted by 442 Millwall fans - at times perhaps could not quite believe the path that this ding-dong game took.
The Lions were dominant for vast periods and started with a conviction to their attacking play, but just could not find the end product in an opening half in which they peppered the home goal with countless crosses.
Neil Harris' charges conjured two good scoring chances in the opening three minutes. A foul on Fred Onyedinma on the edge of the penalty area had Williams, Joe Martin and Shane Ferguson queuing up to try their luck from the resulting free-kick. It was Williams who eventually took charge, but disappointingly curled his effort over the bar.
Former Shaker David Worrall then had time to pick out Harry Smith at the back post with a great delivery, only for the striker to steer his header wide of the target.
There was controversy, however, as the game approached the 15-minute mark when Onyedinma went to ground. Referee Jeremy Simpson initially pointed to the spot, but following a brief discussion with his linesman, awarded a goal-kick instead to the clear disbelief of the visitors.
Twice Maher tested The Lions' resolve with inviting deliveries as the home side took heart from this, but twice Vaughan was thwarted sending his first header wide of the upright and seeing his second deflected for a corner.
By the halfway stage Millwall were just edging the match in terms of possession and a little flurry of three corners in as many minutes saw Harry Smith twice get on the end of good crosses from Ferguson, only to direct his headers off target.
Onyedinma was a whisker away from capitalising on another moment of hesitancy in the home defence only for the boot of keeper Williams to sweep the ball clear. Mahlon Romeo had a shot blocked, corner after corner went into the danger zone and Smith sent another header wide as Millwall attacked relentlessly, but with no return for their pressure.
Kelvin Etuhu had Bury's chance when, in a three-on-one counter attack, he failed to pick out either of his two unmarked team-mates and instead went for goal himself, hitting a shot that almost apologetically bobbled into the hands of Jordan Archer.
It was a rare moment of action for the Lions keeper, with the goalmouth action remaining firmly at the other end.
A reckless challenge by Craig Jones on left-back Martin brought a yellow card for the Bury man and handed a chance for The Lions in the last minute of a dominant first-half from the visitors. Worrall swung the ball over from the left, Onyedinma slipped his marker only to power a header narrowly over the bar.
Having been on the back foot for so long, Bury had to try something different and introduced debutant Jacob Bedeau and Andrew Tutte at the start of the second-half.
However Millwall picked up where they left off as they tried to grab that all important first goal. Smith just couldn't sort his feet out to get a shot in from Ferguson's corner, then saw a free header from another Ferguson deadball drift harmlessly wide.
Bury stunned the visitors just past the hour-mark when, having been on the backfoot for so long, Vaughan was picked out at the back post by Danny Mayor and sent a looping header over Archer. The ball smacked the crossbar and bounced back down over the line. Could this be the bit of luck Bury had needed to bring their miserable run of results to an end?
It certainly looked that way and the home side now had their tails up. Scott Burgess lashed the ball over the bar with the goal at his mercy but then atoned for his miss on 67 minutes with a perfectly weighted through ball on the counter attack to pick out team-mate Vaughan, who grabbed his second of the game with a crisp, low finish.
Bury were in dreamland - then in despair - within two minutes. Having forged a 2-0 lead, albeit completely against the run of play, Maher's moment of madness proved costly and having reduced the arrears to 2-1, it was game on again for Millwall.
A textbook downward header from Onyedinma was clawed out by keeper Williams, who then bravely saved amongst a cluster of boots as Bury were put under pressure once more.
Lions boss Harris, who had already introduced O'Brien, then introduced Butcher and Alfie Pavey sensing that the home side were there for the taking - and he was right.
Butcher was perfectly placed to get on the end of yet another searching delivery, this time a Ferguson free-kick, to nod home the equaliser for his second goal in a Lions shirt. Ironically it was the midfielder's second goal of the season against Bury, having scored for previous club Burton against the Shakers in the EFL Cup back in August.
The celebrations that marked Butcher's goal were nothing, however, like the pandemonium that greeted O'Brien's dramatic last-gasp winner.
Time was running out for Harris' men as the game entered the third of four minutes of injury time, but Onyedinma, who had rung rings round the Bury defence all afternoon, drilled in a cross from the right and there was O'Brien to clip home superbly into the bottom corner.
Off came the shirt as O'Brien was engulfed by jubilant travelling fans, and although he earned a booking for his celebrations, nothing was going to dampen his joy, or that of Millwall's comeback kings, with a win that moves The Lions to within one point of the top six.
Bury: Williams, Jones (Bedeau, 46'), Etuhu, Kay, Mayor, Pope, Vaughan, Danns (Tutte, 46'), Soares, Burgess, Maher. Subs not used: Dudley, Rachubka, Hope, Miller, Styles.
Bookings: Jones (44mins), Kay (70mins), Etuhu (90+5')
Sending off: Maher (70mins)
Scorer: Vaughan (61, 67')
Millwall: Archer, Romeo, Martin (Pavey, 83'), Craig, Webster, Worrall (O'Brien, 62'), Williams, Abdou (Butcher, 74'), Ferguson, Smith, Onyedinma. Subs not used: King, Cummings, Thompson, Mbulu.
Bookings: Smith (70'), O'Brien (90+3')
Scorers: Williams (70' pen), Butcher (86'), O'Brien (90+2')