Molinari defied the blustery conditions to post the only bogey-free round of the day, carding 16 pars and two priceless birdies, including the clincher at the final hole which earned him a two-shot win and his maiden major title, the first Italian to achieve the feat, at the age of 35.
His composed performance, the highlight of which was a sublime short-game, earned him his third victory of a golden run of form which began at the BMW PGA Championship in May, while he also ended the American stranglehold on the major championships.
Tiger Woods and Rory McIlroy were among six players who had at least a share of the lead during an enthralling afternoon on the historic Angus links, but their challenges came up just short along with English pair Justin Rose and Eddie Pepperell.
Jordan Spieth’s bid to become the first back-to-back champion in a decade was ultimately scuppered by a double-bogey seven at the sixth and a cold putter throughout, and he would finish four off the pace after a 76 while Kevin Kisner and Xander Schauffele shared second with McIlroy and Rose.
But it was to be Molinari’s day in the limelight as the red-hot Italian avoided the card-wrecking mistakes that beset his fellow contenders, grinding out par after par while displaying a deft touch around the greens and holing a series of clutch putts to keep himself firmly in the hunt.
He completed a full set of pars on the outward half to trail Woods by one at the turn after the 14-time major champion birdied the fourth and sixth to hit the top of the leaderboard and set the pulses racing among the record crowds for an Open at Carnoustie.
The Woods express then hit the buffers when he scrapped his way to a double-bogey six at the 11th and dropped another shot at the next, while Molinari continued his run of pars until breaking the streak with a nerveless two-putt for birdie at the long 14th.
Molinari’s excellent four took him to seven under and one ahead of a suddenly-resurgent McIlroy, who had struggled to the turn in an erratic 37 before he surged back into the reckoning with a birdie at 11 and a huge 60-foot putt for eagle at the 14th.
But McIlroy was unable to improve on six under and left a birdie putt short of pace at the last to complete a 70 which gave him a share of the clubhouse lead with Rose, who had earlier birdied the 18th for the fourth consecutive day to return a 69, just two days after holing from 12 feet on the same green just to make the weekend.
With Spieth unable to recover from his front-nine mistakes, the worst being a carve into a bush at the sixth, Schauffele remained the biggest threat to Molinari as he recovered from an outward 40 with birdies at the 10th and 14th, where his 15-foot eagle putt hung on the back lip and refused to drop south.
However, Molinari’s nerve held on the 72nd hole as he hammered an arrow-straight tee-shot and clipped a sublime wedge to three feet before rattling in the winning putt and returning to the clubhouse to face an anxious wait to see if Schauffele could catch him.
But the 24-year-old American took himself out of the running with a bogey at the treacherous 17th, and he missed out on outright second when his birdie putt at the last lipped out on the right with Molinari in tears of joy in the winners’ enclosure.
Woods, meanwhile, managed to lift himself back to within a shot of the lead with a great putt for birdie at 14 having opted to chip his third despite being on the green but, like McIlroy, he had to settle for four closing pars and his third 71 of the week.
Kisner started the day in a tie for the lead before a double-bogey at the second started a downward trend as he laboured to the turn in 40, and a one-under inward half was not enough to mount a serious threat to Molnari at the end.
Round of the day went to the popular Pepperell, who upstaged playing-partner Phil Mickelson and defied the effects of a self-confessed hangover to card five birdies and just one bogey in a 67 which lifted him 30 places up the leaderboard and into the tie for sixth – comfortably his best performance in a major.
As for Spieth, he got off to a solid start with four straight pars before his problems began at the fifth, and worse was to follow at the next when he carved an ambitious second into a bush and was forced to take a penalty drop which all added up to a seven.
The defending champion missed a series of birdie chances over the remainder of his round, and his day was summed up when he three-putted from 10 feet to bogey the 15th before his shoulders sagged further following another dropped shot at the penultimate hole.
Spieth, who remains without a victory since his win at Royal Birkdale 12 months ago, closed out his defence with a par at the last to finish four under and complete yet another riveting Sunday at The Open, with the final honours going to Molinari and teenage Scot Sam Locke, the winner of the Silver Medal as leading amateur.