After starting the day four shots ahead of Smith, Rory McIlroy finished two strokes behind in third after signing off a bogey-free 70.
It meant heartbreak for the Northern Irishman who, looking to end an eight-year major drought, saw a second Claret Jug win slip through his fingers after a day of missed putting opportunities.
Yet while the 33-year-old subsequently birdied just once more, up ahead Smith — having already doubled that tally by his fifth hole — burst through the back nine with a run of five birdies before adding one more at the 18th.
With Young draining a dramatic final eagle just moments earlier, the Australian’s eighth and final birdie of the round spared him a playoff, his victory assured after McIlroy failed to make the speculative eagle chip needed to draw level.
Overcome with emotion and almost unable to get his words out during the trophy presentation on the 18th tee, Smith opened his press conference simply welcoming the ability to breathe again.
“To win an Open Championship in itself is probably going to be a golfer’s highlight in their career,” Smith told reporters.
“To do it around St Andrews is just unbelievable. This place is so cool. I love the golf course. I love the town.”
The triumph sees Smith become the first Australian to lift the Claret Jug in almost 30 years, after Greg Norman won at Royal St George’s in 1993. Etching yet more history, his four-stroke overhaul matched the largest comeback win at St. Andrews, most recently achieved by John Daly in 1995.
It sealed a remarkable final day fightback for Smith, whose disappointing 73-shot round Saturday had spoiled an opening 67 and a scintillating 64 that had seen him hold the lead heading into the weekend.
Yet far from ruing giving himself extra work, Smith revealed it was a “good thing” that he had been trailing ahead of the deciding day.
“It’s very easy to get defensive out there and keep hitting it to 60, 70 feet, and you can make pars all day, but you’re not going to make birdies,” he said.
“I think it was a good thing that I was definitely behind. I think my mindset would have been a touch different coming in, especially on that back nine, if I was ahead.”
‘It’s not life or death’
Third place marks a repeat of McIlroy’s finish at St. Andrews in 2013. Competing in his 13th Open Championship, the Northern Irishman had made no secret of his “dream” to win at the ‘home of golf’ to add to his Claret Jug lifted at Royal Liverpool in 2014.
He arrived at the Old Course riding a wave of local support as well as form, having finished runner-up at the Masters and inside the top eight at the other two majors this season.
That form was well on show in McIlroy’s stellar tee driving and approach play throughout the day, but the 21-time PGA Tour winner was ultimately undone by his short game as he failed to one-putt from the green through the entirety of the final round.
“I’ll rue a few missed putts that slid by, but it’s been a good week overall,” McIlroy told reporters.
“I’m playing some of the best golf I’ve played in a long time, so it’s just a matter of keep knocking on the door, and eventually one will open.
“At the end of the day, it’s not life or death. I’ll have other chances to win the Open Championship and other chances to win majors. It’s one that I feel like I let slip away, but there will be other opportunities.”
“I certainly appreciated the support, and it was incredible to be cheered along all 72 holes, but I didn’t let that put me under any more pressure,” he said.
“I’m trying to do it for me at the end of the day. Yes, it’s great to get the support, but the happiest person in the world if I won that Claret Jug would have been me.”
Meanwhile, Hovland reflected on an “anti-climatic” close to what had been a hugely impressive performance in just his second Open outing. After carding an unblemished scorecard Saturday, the 24-year-old bogeyed three times — and birdied just once — during the final round.
Despite only turning professional in 2019, the Norwegian looked at home contending atop the leaderboard throughout the week. Though unable to maintain the pace needed to fulfill his dream of a first major, the fourth-placed finish marked his best result at a major to date after 12th placed finishes at last year’s event and the US Open in 2019.
“I was expecting I was going to hang in there for a little bit longer,” Hovland told reporters.
“Just a little disappointed I didn’t have it today, but it was a great experience today and obviously yesterday as well. The whole week was a good learning experience, and I feel like I’m going to get better from it.”