MURRAY Wallace scored a sensational injury-time winner after Millwall had twice come from behind to dump Everton out of the FA Cup.
Wallace poked home in the 94th minute to spark wild scenes at The Den as Millwall under Neil Harris knocked a fourth Premier League side out of the competition in two years.
Richarlison put Everton in front with a shot from outside the box in the 43rd minute that went under Jordan Archer's dive, before Lee Gregory headed Millwall level two minutes into first-half injury-time.
The Toffees regained the lead with 17 minutes left through substitute Cenk Tosun, but Millwall found a second equaliser when Jake Cooper forced the ball in with a suspicion of handball.
And with almost the last kick of the game, the Lions scored off a third set-piece, Wallace finishing from six yards.
With the rain and the muddy pitch and Millwall making it so difficult for Everton, it couldn't have felt more like a proper FA Cup tie.
The Lions didn't deserve to be behind but had the perfect response through Gregory's clever finish over England goalkeeper Jordan Pickford.
It looked like Everton had broken Millwall's resistance with Tosun's goal, but Millwall again found a way.
While Everton showed the strength of their bench, Millwall had fewer options, promoting two under-23s to the match-day squad. They also had 35-year-old Steve Morison, who would make a crucial late difference.
The amount of work they got through was immense, unsung heroes such as Ryan Tunnicliffe and Wallace, the latter who kept Ademola Lookman so quiet, doing so much to ensure their side got one more chance.
It had the feeling something special could happen, and a draw and a trip to Goodison felt like reward for such resilience.
But there was more. Shaun Williams curled a set-piece into the box, and Wallace was the Lions' match-winning hero.
Millwall were without 10 first-team players, Jed Wallace a late absentee through injury.
Under-23s Jethro Hanson, a midfielder, and Gary Alexander, the son of George, were in the first-team squad for the first time.
Everton named close to their strongest side.
Millwall: Archer; Romeo, Hutchinson, Cooper, M Wallace; Tunnicliffe, Williams, Leonard; O'Brien (Skalak, 87), Gregory (Pearce, 96), Ferguson (Morison, 89). Subs: Martin, Pearce, Meredith, Morison, Hanson, Alexander, Skalak.
Shane Ferguson and Aiden O'Brien started in wide attacking positions supporting lone striker Gregory, with Ryan Leonard the most advanced central midfielder in a 4-3-3 formation.
Millwall had a chance in the eighth minute when Cooper got free in the box but he headed Ferguson's free-kick wide.
Five minutes later Lucas Digne headed off the line after Shaun Hutchinson had nodded another Ferguson free-kick from the right across goal towards the far corner.
Gregory had a difficult task up front on his own and when Leonard cleared at one point in the first half there was no Lions player within 20 yards of the striker.
The teeming rain made it a scrappy game. Millwall defended with their usual discipline, Everton seeing more of the ball but it was mostly lateral in front of the Lions. One laborious move ended with Richarlison crossing to no one at the back post.
Lions fans were then riled when Richarlison stayed down after a strong tackle by Hutchinson, but Michael Oliver didn't give anything to the Brazilian, who was booed the next time he was on the ball.
Millwall were almost authors of their own downfall nine minutes before the break when Archer's mis-kick fell to Gylfi Sigurdsson, but the Iceland international wasn't sure enough with his touch and Cooper nipped in to clear.
Richarlison was the Toffees' most dangerous player, but even he couldn't believe his luck when he fired in a shot from 25 yards that Archer had covered only to let the ball slip under him.
There was probably no one more relieved at The Den than Archer when Gregory brilliantly looped a header over Pickford after Cooper, standing 25 yards from goal, had flicked on Williams' free-kick. The Lions deserved to go in level at the break.
Gregory continued to lead the line brilliantly, now up against Kurt Zouma who had come on at half-time for Yerry Mina, and after he darted into the box the ball went back to Romeo who crossed but Wallace, up from left-back, couldn't make proper contact with his header.
Very little had been seen of Lookman, but he came to life in the 55th minute to set up Sigurdsson whose shot from outside the box deflected for a corner. Unlike Millwall, Everton could not take advantage of their set-pieces.
Gregory could have perhaps shot when he found himself free in the box instead of trying to roll a ball through to Williams. He over-hit it and Everton were let off the hook.
The sense that maybe an upset could be on the cards increased as the rain heavily fell and the noise levels rose, the first chants of 'Millll' thundering around the ground.
But Everton started to find gaps in the Lions' defence and when Sigurdsson picked up possession 30 yards out he spotted Tosun's run. The pass was perfect and the striker rolled the ball into the far corner for 2-1.
The Den was as intense as it's been at any time in Neil Harris' tenure. The home fans urged their side forward and when Ferguson curled in a free-kick from the right with 15 minutes left Everton failed to clear, the ball ricocheting to Cooper who had his sixth of the season. There was a brief wait as referee Oliver consulted with his assistant. There was a video assistant referee scheduled at six fourth-round ties but not here. Everton thought Cooper had handled, the officials disagreed.
A replay at Goodison loomed, but Millwall had other ideas. Morison came on to win a free-kick, and Wallace made another special Den memory to send his side through.
Image: Millwall FC