Femi Azeez scored twice as Millwall caused an upset by dumping Championship rivals Leeds out of the FA Cup to progress to the fifth round for the first time since 2018-19.
Alex Neil’s in-form Lions arrived at Elland Road on the back of three straight league wins and they proved too strong for an under-strength Leeds outfit in front of a 34,923 crowd.
Whites boss Daniel Farke made 10 changes and it showed as winger Azeez opened the scoring in the 30th minute before grabbing his second 10 minutes into the second half.
Visiting goalkeeper Liam Roberts enjoyed an outstanding game and saved a penalty from Leeds defender Pascal Struijk on the hour as Millwall won the first-ever FA Cup meeting between the sides.
Leeds are top of the Championship and remain well placed to reach the Premier League but this was a major disappointment as their 14-match unbeaten run in all competitions was ended.
Leeds won 2-0 at Coventry in midweek but captain Ethan Ampadu was the only player retained with 17-year-old academy graduate Sam Chambers handed his first senior start.
The teenager impressed on the right flank and threatened early on with a powerful strike from 14 yards which flew over the visitors’ crossbar.
In the 22nd minute, Chambers escaped down the right flank and delivered a dangerous cross to Willy Gnonto, whose close-range shot was repelled by Roberts.
But Millwall led when Leeds lost possession inside the right channel and Azeez advanced forward before cutting inside and hitting a right-foot shot which deflected off Josuha Guilavogui and into the far corner.
In the 36th minute, Millwall went agonisingly close again when Ampadu was dispossessed and goalscorer Azeez thrashed a fierce shot against the underside of the crossbar.
The ball bounced out to Luke Cundle who could only send his header wide from inside the six-yard box.
Moments later, Leeds ventured upfield and Chambers showed neat footwork to create the space to hit a left-foot shot which drew a smart save from Roberts.
In the 54th minute, Gnonto found Largie Ramazani and he hit a low, left-foot shot from 16 yards which Roberts did well to tip round his post for a corner.
But moments later, Millwall had their second when Guilavogui was dispossessed on halfway before Azeez broke down the left flank and hit a low, left-foot shot which beat Karl Darlow at his near post.
On the hour Leeds were awarded a penalty when Gnonto went down under Cundle’s challenge.
Struijk stepped up but Roberts did superbly to dive to his left and tip the ball onto the post before Millwall cleared the danger.
Farke made five changes but Roberts remained in inspired form as Leeds slipped to their first home defeat since last September.
