|Gueye 79, Hooiveld 87||Venue: The Den
MILLWALL fought back from a goal down to defeat ten-man Charlton and keep their survival hopes alive.
The Lions spurned a glorious chance to take the lead when Chris Solly's handball resulted in a red card and a penalty but Lee Gregory's effort was saved.
And despite their numerical disadvantage, the Addicks took the lead in the second half when Alou Diarra guided in Morgan Fox's cross with a clever flick.
But substitute Magaye Gueye drilled in the equaliser from a tight angle and then his shot was steered home by Jos Hooiveld to put Millwall ahead.
The Lions saw out six minutes of additional time to secure their first home victory since October and keep them within touching distance of Rotherham, who lost at Birmingham.
Fellow strugglers Wigan and Fulham were also beaten to cap a fine afternoon for Neil Harris, who tasted victory for the first time as interim manager.
Harris named an unchanged side following the 2-2 draw with Brentford before the international break, with Gregory and O'Brien continuing their partnership up front.
Nicky Bailey, who had returned to full training at the start of the week, was passed fit to take his place on the bench, but Paris Cowan-Hall and Lee Martin missed out.
Harris had promised fans would see an "aggression that the situation demands" from his side and sure enough Millwall burst into life from the first whistle.
Ed Upson, whose inch-perfect assist created Gregory's goal against the Bees, almost repeated the trick but on this occasion his floated diagonal pass drifted just beyond the striker.
Upson's dangerous free kick was then flicked behind for the first of three corners in a row, the second of which came to Sid Nelson whose shot deflected behind.
The best of the Lions' attacking play was all going through Upson and he started and finished an incisive move, powering a header over the bar from Dan Harding's cross.
Upson broke forward again in the 23rd minute, skipping past Fox on the byline before sending in a low cross which the Addicks eventually scrambled clear.
On a rare Charlton break, former Den trialist Chris Eagles prodded into the side netting from Johann Gundmundsson's clever lob.
But Millwall were by far the dominant side and, after Martyn Woolford's effort was scrambled off the line, O'Brien's goal-bound follow-up was handled by Solly.
The Charlton captain had already been booked but referee Mick Russell had no alternative but to show the right back a straight red card.
But Gregory was foiled by Henderson from 12 yards, his low spot-kick not placed far enough into the corner.
The visitors brought on Andre Bikey in an attempt to shore up their defence but the Lions continued to create the better chances.
Woolford went close to turning in Jimmy Abdou's deep cross, Upson was denied by Henderson's one-handed save and O'Brien shot over the bar during a spell of dominance.
After an uneventful start to the second period, Charlton had the first attack when they broke forward and Gudmundsson curled narrowly wide of the top corner.
At the other end, Upson volleyed over from a corner before Williams drew another fine save from Henderson, who tipped the ball behind.
The Addicks went ahead in the 67th minute when Fox jinked into a yard of space before delivering a low cross to the near post which Diarra cooly diverted beyond David Forde.
Harris responded to the goal by bringing on Stefan Maierhofer and Bailey for Dan Harding and Upson, who was struggling with a tight hamstring.
And Gueye, who Harris had introduced before Charlton took the head, smashed in the leveller from what seemed an impossible angle to set up a grandstand finish.
Simon Church almost restored the visitors' lead but he nodded wide when well-placed as the Lions breathed a huge sigh of relief.
And Hooiveld completed their comeback with an instinctive finish from close range, diverting in Gueye's shot to send The Den into raptures.
Williams almost added a third goal in stoppage time when Henderson was caught upfield at a Charlton corner, but his miss proved immaterial as Harris' side held on.