After a tense, tight derby encounter, the midfielder popped up in the final minute of added time to nod home Patrice Evra's superb cross and move the Reds to within a point of Chelsea, ahead of the league leaders' late-afternoon trip to Tottenham.
Amid the Reds' ongoing chase for a fourth straight title, the subplot of City's challenge for local and, ultimately, national supremacy had seemed set to hog the headlines. But Scholes had other ideas and just a day after penning a one-year contract extension, the 35-year-old illustrated his enduring value not only with his winner, but by dictating play in a masterful midfield performance.
Of United's three pre-match injury doubts, two recovered sufficiently to join the starting XI. Wayne Rooney and Ryan Giggs were both available, but Rio Ferdinand's groin injury prompted a return for Jonny Evans alongside Nemanja Vidic in the centre of defence.
Both sides started the game with evident intent to attack. Darren Fletcher fired a 25-yard effort inches wide of Shay Given's post, with the Irishman well beaten, before Carlos Tevez's top corner free-kick drew a fine full-length catch from Edwin van der Sar.
Despite coming out of their corners swinging, both sides quickly displayed an awareness of the potential cost of failure. United bossed possession by virtue of an extra man in midfield, but refused to overcommit in support of Rooney, while City sat deep, costing themselves the chance to offer quick, accurate service to Tevez and Emmanuel Adebayor.
Scholes scuffed a shot wide from 25 yards, before a slip from Vincent Kompany allowed Rooney to race into the Blues' area. The Belgian's blushes were spared, however, when Kolo Toure blocked two attempted pull-backs from the striker. That characterised a first half largely comprised of chances snuffed out in their infancy. Giggs' in-swinging free-kick and Craig Bellamy's low ball across the six yard box both begged for conversion, but were instead left unfulfilled.
United spurned the two clearest openings of the half in its final five minutes. Both chances were created by the industry of Antonio Valencia, who held off Wayne Bridge to head across for Rooney, only for the striker to fire uncharacteristically off-target, before the Ecuadorian's low cross was stabbed straight at Given by Giggs.
Level, but having been comfortably outplayed, City began the second half with greater purpose. Kompany and Adam Johnson both picked up yellow cards in quick succession, before a counter-attack from the home side was wasted by Bellamy, who blazed wide instead of squaring for Tevez.
Despite that scare United were still bossing matters, and the Reds' need for victory was layed bare when Nani replaced Gibson. Roberto Mancini responded conversely, sending on midfielder Patrick Vieira for winger Johnson. The two substitutes were soon involved. A patient United move culminated in Giggs sliding an enticing ball into the area, which Nani slid wide under heavy pressure from Vieira. As the game entered its final 20 minutes, both teams began to open up.
Gareth Barry, largely anonymous in the midfield battle, had a glorious chance after latching onto Adebayor's neat through-ball, but the England midfielder opted to cut inside and tumble under Neville's attentions rather than pull the trigger. No penalty met his half-hearted appeal, and as play continued he was indebted to Given's
close-range save from an attempted lob by Giggs.
Dimitar Berbatov replaced Rooney, who looked short of full fitness, while Valencia made way for Gabriel Obertan as United continued to press. The Bulgarian's first contribution was almost a telling one, as his glancing header from a Nani cross sneaked just past Given's post.
At the other end, Vidic produced two brilliant interceptions in quick succession to keep City at bay, first flicking a cross away from the lurking Nedum Onuoha, then toe-poking away the danger in an almighty goalmouth scramble.
United's menace continued to linger, though. Agony was etched across Giggs' face when he just failed to reach Nani's cross in the final minute of normal time, but those emotions flipped entirely just as time seemed to be up.
Evra led one final foray down the left flank, exchanged passes with Obertan and floated a superb cross into the centre of the City area. There, onrushing in trademark fashion, was Scholes to execute a perfect header which nestled just inside Given's post.
The goal prompted near-feral scenes of delight among players, staff and supporters of a Red persuasion. The saying goes that lightning never strikes twice. How about thrice? Just as the Blues had seemed set to curtail the Reds' hunt for history, United struck a winner in injury-time for the third of four meetings this season. For now at least, Manchester resounds to status quo, rather than new order.
The bigger picture for United is one of silverware. There must be favours from other clubs in order for history to be re-written, but if the champions are to be dethroned, it won't be without a fight.