Smith overturned a four-shot deficit courtesy of his second 64 in the space of three days, the 28-year-old from Brisbane finishing 20 under par to beat the previous record on the Old Course of 19 under set by Tiger Woods in 2000.
An eighth birdie of the day on the 18th gave Smith a one-shot victory over playing partner Cameron Young, who eagled the final hole, with 54-hole co-leader Rory McIlroy a shot further back following a closing 70.
“I think to win an Open Championship in itself is probably going to be a golfer’s highlight in their career. To do it around St Andrews I think is just unbelievable,” said Smith, who declined the chance to deny reports linking him to the Saudi-backed LIV Golf series.
“This place is so cool. I love the golf course. I love the town. To have the 150th Open here and to walk away with the win is just something that I have dreamt of.
“It’s unreal to look at these names on this trophy and then add mine, I’m lost for words. I’m definitely going to find out how many beers fit in this thing, that’s for sure.”
Asked about failing to convert previous chances to win a major – he finished runner-up in the 2020 Masters and was third at Augusta National in April – Smith added: “I’ve definitely kicked myself a couple of times over the past few years.
“To do it the way I did today was pretty cool, to be back and really apply pressure, keep holing putts. It was awesome.
“The course was exactly how an Open Championship should be played, firm and fast. It was absolutely unreal. I had a lot of support out there, especially the Aussie guys who really kept me going out there. This one’s for Oz.”
Asked about the possibility of joining the breakaway LIV Golf series, which is spearheaded by fellow Australian and two-time Open champion Greg Norman, Smith said: “I just won the British Open and you’re asking about that.
“I think that’s pretty not that good.”
Pressed on whether he was interested in joining, Smith added: “I don’t know mate. My team around me worries about all that stuff. I’m here to win golf tournaments.”