Harlequins staved off a spirited Gloucester comeback to seal a 28-24 victory and move above their opponents to sixth in the Premiership table.
In front of a mammoth crowd of 77,567 at Twickenham, Quins led 28-10 with less than 20 minutes remaining, but two converted tries hauled Gloucester back into it, with the hosts forced to play the final 10 minutes a man light.
Quins led 11-3 at the break with Joe Marchant's try added to by two Ruaridh Jackson penalties. Greig Laidlaw's three-pointer was the only score for the visitors, who had Jonny May sin-binned for a deliberate knock-on late in the first half.
Jack Clifford went over in the first minute of the second period for Quins, but Gloucester responded through Gareth Evans.
Marchant's second try and five more points from Jackson had Quins in control heading into the final quarter, but James Hook's score gave Gloucester hope.
That hope turned into genuine belief as Motu Matu'u crossed the whitewash - Clifford sin-binned for a professional foul in the build-up - but Quins were able to hold on and take the spoils from an enthralling encounter.
FULL TIME and Harlequins hold on to beat Gloucester in another Big Game thriller!!!! pic.twitter.com/LbTGhVzKIb-- Harlequins (@Harlequins) December 27, 2016