Midfielder bags two deflected goals to put Kop 19 POINTS clear of Mourinho's sorry visitors - after Lingard had briefly cancelled out Mane's opener.
SUB Xherdan Shaqiri's lucky late double put Liverpool top - as outplayed Manchester United fell 19 POINTS off the pace.
Jesse Lingard soon bundled United level after Sadio Mane chested down to slot Liverpool's deserved opener on 24 minutes - but in the end class, pressure and the sheer volume of the Kop's incredible 36 chances on goal paid off.
Swiss midfielder Shaqiri saw low shots deflect in on 73 and 80 minutes for a Kop victory that could easily have been doubled.
Liverpool had 65% of the possession and more scoring opportunities than United have conceded for 14 seasons - without ever quite reaching top gear.
And an even bigger indictment of United's latest dull, tame display was how little fervour they created against their fiercest rivals.
Old Trafford boss Jose Mourinho had labelled Liverpool lucky for the way they won three of their past four games before this one-sided clash.
And although Shaqiri's finishes were, of themselves, a tad fortunate, Mourinho must know such moments will come if the opposition pepper your goal with crosses and half-chances.
The under-fire manager admitted straight afterwards: "We couldn't cope with their fantastic intensity."
Tellingly, perhaps, whereas Mourinho brought on mediocre grafter Marouane Fellaini at half-time for youngster Diogo Dalot, Liverpool were able to introduce mercurial crafter Shaquiri with 20 minutes remaining.
Fellaini was as muted and ineffective as his colleagues - whereas Shaqiri buzzed around the fringes of the United box as Liverpool came forward from all angles.
And possibly the only solace for Mourinho was that much-maligned centre-backs Eric Bailly and Victor Lindelof stood up to all the pressure reasonably well.
Ultimately, though, the duo's resilience was in vain - leaving United 11 points adrift of fourth-placed Chelsea and eight behind Arsenal.
