The City midfielder came on as a half time substitute in the Red Devils’ second Group B game and helped turn the tide after the Danes had gone in 1-0 up at the break thanks to Yussuf Poulsen’s second minute goal.
It was De Bruyne’s first competitive action since he was forced off during last month’s Champions League final against Chelsea with injuries to his nose and eye.
And the 29-year-old’s impact was almost instantaneous as he set up Thorgan Hazard register a 54th minute Belgium equaliser with a sumptuous pass.
It was De Bruyne’s eighth assist at a major championship – and saw the City man become the only European player to assist a goal in each of the last four major tournaments (World Cups and Euros) in 2014, 2016, 2018 and 2020.
De Bruyne’s brilliance was then further illustrated on 70 minutes as he struck a quite wonderful winning goal for Roberto Martinez’s side.
After some impressive Belgian build-up play, Eden Hazard found De Bruyne in space and the double PFA Player of the Year slammed home a perfect left-footed shot into the bottom corner from 20 yards out.
It was a total transformation from the opening 45 minutes on what was a hugely emotional occasion in the Danish capital.
Both sides briefly took a break from the action on 10 minutes to applaud and pay tribute to Christian Eriksen in the wake of the Danish midfielder’s cardiac arrest last weekend.
The hosts had made the best possible start, racing into a second minute lead in Copenhagen through Yussuf Poulsen’s strike.
A Jason Denayer error saw the former City defender inadvertently hand possession to Denmark's Pierre-Emile Hojbjerg who, in turn, fed Poulsen before the unmarked striker fired home.
Denmark could have added to that lead but spurned a number of chances and were then made to pay the price following the introduction of De Bruyne.
Even so, in what was another superb encounter, Denmark almost summoned up a late equaliser with Martin Braithwaite hitting the bar with an 88th minute header.
But, once again, the impact of brilliant De Bruyne prove decisive as Belgium held on for a victory which means they are assured of their place in the last 16 knockout stages.