United were in front but needing calming despite Cristiano Ronaldo's first-half penalty when Giggs kept his nerve to coolly slot home Wayne Rooney's through ball.
A quarter of an hour earlier, Giggs' had been introduced for his 758th United appearance, equalling a milestone left by Sir Bobby Charlton that will surely be eclipsed in Moscow on May 21.
But all Giggs will care about is adding to a medal collection that continues to expand, containing all 10 championships won under Sir Alex Ferguson, part of an overall United haul of 17, one adrift of Liverpool, who Ferguson has vowed to overtake.
Few would begrudge the Red Devils their latest success, even if the free-flowing attack that has propelled them to glory by two points over Chelsea - who drew 1-1 with Bolton - was strangely muted.
Certainly anyone still daring to suggest Steve Bruce was happy enough to do his old club a favour clearly was not inside a stadium where, contrary to stated wisdom, the vast majority wanted a home win.
And how Wigan did their supporters proud as they controlled possession for long periods and enjoyed the majority of chances.
Emile Heskey was a particular thorn in the side of Rio Ferdinand and Nemanja Vidic and, with Antonio Valencia providing flashes of inspiration from the flanks, United were wobbling.
Had Chelsea known the strife their rivals were in and taken advantage in those tense early minutes, United may have toppled.
Instead, Michael Brown, Jason Koumas and Marcus Bent all failed to convert half chances and Chelsea, with longer-term problems concerning John Terry to deal with, could not seize the early initiative.
Not for the first time in recent weeks, Ronaldo had been a subdued force until his moment of destiny arrived and allowed him to equal Alan Shearer's Premier League best haul of 31.
The Portugal winger is still to produce the one stand-out performance on a day of high importance that will silence his remaining critics.
But, with the pressure starting to increase, Ronaldo was the coolest man in the stadium, sending Chris Kirkland the wrong way after Boyce had clipped Wayne Rooney.
As Sir Alex Ferguson had listed Rooney as no better than having the chance of a place on the bench 48 hours earlier, the striker's presence in United's starting line-up was a major surprise.
Like Ronaldo, Rooney toiled for long periods without having an impact but as Paul Scharner let the ball slide under his foot, Ferguson's decision to select the England man was fully justified as he was onto it in a flash.
A posse of Wigan players, Boyce among them, surrounded referee Steve Bennett to complain, although in truth they had a more plausible argument when Paul Scholes barged Wilson Palacios over by the touchline a couple of minutes later.
As the tenacious midfielder had already been booked for a foul on the same man, Bennett would have been fully justified in giving the afternoon a dramatic twist by pulling out a red card.
Instead, the official, harangued by Ferguson for dismissing Ronaldo at Portsmouth earlier in the season, opted to issue a final warning, which merely reinforced the belief that United would be champions.
United certainly began the second-half as if they believed it.
Kirkland denied a thunderous Ronaldo free-kick and goalbound efforts from Rooney and Carlos Tevez.
It formed past of a frenzied period which should have seen United awarded a penalty for Titus Bramble's ill-advised lunge on Scholes and Rooney booked as he launched a volley of abuse at Bennett for a free-kick awarded against him.
At least for the sake of United's nerves, the action was taking place around the Wigan goal but by the time Giggs was introduced, the Latics had revived and Emile Heskey planted a header on the roof of the visitors' net from Koumas' free-kick.
But United were not to be denied and 10 minutes from time, Rooney provided the killer pass for Giggs to wrap up yet another title and allow minds to wander towards the Luzhniki Stadium in 10 days' time when they intend to leave Chelsea heartbroken once more.www.soccernet.com
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