Full-time from The Den
Lions boss Ian Holloway and his assistant Marc Bircham were then sent to the stands moments after Lee Martin had reduced the arrears with 18 minutes remaining, but the final twist in the tale came in the 88th-minute when Williams lashed home an equaliser.
When Rudy Gestede put Rovers 2-0 ahead four minutes after the red card it looked to be game over and three points in the bag for Gary Bowyer's men.
On a night of high drama at The Den, Lions defender Andy Wilkinson was dismissed in the 63rd-minute for a foul on Ben Marshall with The Lions already trailing to Shane Duffy's 37th-minute opener.
Shaun Williams grabbed a dramatic late leveller as 10-man Millwall fought back brilliantly from 2-0 down to secure a share of the points against Blackburn Rovers.
Ed Upson then tried his luck from distance with another long-range effort, but to the frustration of the home fans, his shot whistled wide of the target.
There were no changes made by either team and the start of the second-half and it was Williams, at the heart of the most promising Millwall moves on the night, who drew a smart save from Steele with a low shot that picked up speed on a greasy playing surface.
The heavens opened - and the visiting defence so nearly did too - when seconds before the break another inviting cross from Williams picked out Martyn Woolford, but the latter's glancing header flashed wide of the far post.
However when Shittu was penalised for a foul in a 50-50 challenge with Rudy Gestede eight minutes before half-time, Marshall's free-kick from the right found its way to Duffy who smashed home at the second attempt to give Blackburn the lead against the run of play.
The disbelief and fury amongst the home supporters turned to sheer ecstasy in the final two minutes of normal time when Gueye held the ball up well, played it to Martin whose cross was headed out to Williams and he rifled home an unstoppable shot into the bottom corner from 25 yards.
Holloway made his third and final change replacing Fuller with Gueye with quarter of an hour remaining but just two minutes later both the manager and his number two Bircham were sent to the stands by referee Deadman for persistent dissent.
Spurred by a real sense of injustice - and an awful raking challenge on Fuller that went unpunished - The Lions fans and 10-men alike responded magnificently and Holloway's men gave themselves a lifeline with 18 minutes remaining when Fuller laid the ball off for Martin in the penalty area. Martin did well to control the ball on the slippery surface and produced a crisp finish that gave Steele no chance.
Moments later referee Darren Deadman was reaching for his pocket, brandishing a straight red card to Wilkinson for a foul on Marshall right in front of the Blackburn dug-out. Scott McDonald was sacrificed for Dunne with Millwall's second change of the night, but to make matters worse Rovers doubled their tally just a couple of minutes later when Cairney's cross was met by Gestede, who planted a firm header beyond the reach of David Forde.
Millwall were looking good for an equaliser, and the home crowd were howling for a penalty just before the hour-mark when Fuller went to ground, but play was waved on.
Martin (72mins), Williams (88mins) Scorers:
Wilkinson (63mins) Sending off:
Fuller, (73mins), Williams (87mins) Bookings:
Forde, Wilkinson, Briggs, Shittu, Beevers, Williams, Upson (Gregory, 60mins), Woolford, McDonald (Dunne, 64mins), Martin, Fuller (Gueye, 74mins). Subs not used: King, Webster, Ranegie, Chaplow.
Olsson (83mins) Booking:
Steele, Hanley, Cairney, Rhodes (Varney, 86mins), Marshall (Conway, 81mins), Olsson, Baptiste, Duffy, Tunnicliffe, Evans, Gestede. Subs not used: Henley, Kilgallon, Dunn, Eastwood, Taylor. Duff (37mins), Gestede (65mins)Scorers:
Ref: 8,250 (away 486)Att: