First-half goals from Scott Malone and Lee Martin breathed renewed hope into Millwall's bid to avoid the drop as they struck a blow into Nottingham Forest's Play-Off ambitions on a memorable afternoon at the City Ground.
Although Jamie Paterson reduced the arrears on 53 minutes, Millwall held their shape - and nerve - to ultimately record a thoroughly deserved victory on a day that also saw fellow relegation rivals Charlton lose at home to Reading and Barnsley drop points against Brighton & HA.
Boss Ian Holloway made seven changes to the side that drew with Blackburn Rovers last time out, handing a full debut to striker Stefan Maierhofer and a first start in two months to midfielder Nicky Bailey, who had been sidelined with a back injury.
Alan Dunne came in as skipper to partner Mark Beevers in the heart of a new-look defence that saw Carlos Edwards and Scott Malone fill the respective right and left-back slots.
In the middle Ed Upson returned alongside Bailey, with Lee Martin and Martyn Woolford also back in the first team line-up.
It was Millwall who carved out the first decent scoring chance of the game on nine minutes when Maierhofer was picked out by a diagonal pass into the box by Upson. The big striker controlled the ball before hitting an angled drive that Forest keeper Karl Darlow gathered at the near post.
However there was nothing Darlow could do to prevent The Lions taking a deserved 18th-minute lead when Maierhofer flicked the ball into the path of Malone, and his low fizzer took a wicked deflection off the outstretched leg of Gonzalo Jara and past the wrong-footed keeper.
Three minutes later it was so nearly 2-0 when Woolford's deep cross was met by home defender Danny Collins who sent a powerful header narrowly over his own bar for a corner.
Forest, very well contained by Millwall in the opening 45 minutes especially, registered their first shot on goal 10 minutes before the break with a low scuffer from Radoslaw Majewski that bobbled three yards wide. His effort, and Forest's first-half display, was met with howls of derision by a frustrated City Ground crowd of 20,077.
The Lions grabbed a second, and what proved, decisive second goal on 39 minutes with a splendidly executed effort from Martin. Having picked up the ball on the left he still had plenty to do, but drove forward with purpose and then dispatched a curling shot from 16 yards that nestled into the bottom right hand corner.
Forest introduced Henri Lansbury for Majewski at the start of the second-half, although it was The Lions who nearly added a third in the 48th-minute when a slick move down the left worked the ball to Woolford, who just couldn't sort his shooting feet out and sent an effort bobbling harmlessly wide.
Forest breathed a sigh of relief at that let-off and found themselves right back in the game on 53 minutes. Dan Harding wriggled into a decent position on the left and his inviting cross was met by Jamie Paterson, whose flicked header left David Forde grasping at thin air.
Steve Morison entered the fray for Maierhofer seconds after the latter was booked, and on 68 minutes the sub chested down Malone's cross and hit a rasping, rising drive that was heading for the top corner only for Darlow to fling himself across goal and push his thumping shot over for a corner.
The home side then threw on former Lion Darius Henderson as they went for broke and it was heart in mouth time on 70 minutes when Lansbury curled a free-kick narrowly over from a central position 18 yards out.
Holloway responded by replacing the tireless Bailey with Scott McDonald and then Edwards with Paul Robinson, who took his place in the heart of a re-jigged backline that saw Dunne slotting in at right-back.
It proved to be an extraordinarily nervy finale, including five minutes of injury-time in which it felt as if the clock was going backwards. But The Lions dug deep and head to Wigan Athletic on Tuesday with confidence and belief that the relegation battle is far from over yet.
Nottm Forest: Darlow, Jara, Halford (Wilson, 40mins), Collins(c), Harding, Greening (Henderson, 69mins), Peltier, Osborn, Majewski (Lansbury, 46mins), Paterson, Mackie. Subs not used: De Vries, Gomis, Derbyshire, Cox.
Bookings: Greening (51mins), Lansbury (78mins), Peltier (90+3mins)
Millwall: Forde; Edwards (Robinson, 79mins), Dunne (C), Beevers, Malone; Upson, Bailey (McDonald, 71mins); Martin, Garvan, Woolford; Maierhofer (Morison, 61mins). Subs not used: Bywater, Robinson, Williams, Abdou, Jackson.
Bookings: Maierhofer 59mins), Morison (70mins)
Scorers: Malone (18mins), Martin (38mins)
Ref: M. Brown
Att: 20,077 (away 625)