Cameron Smith came through a thrilling final-round tussle with Rory McIlroy and Cameron Young to claim a maiden major title with a dramatic one-shot victory in The 150th Open
Smith overturned a four-stroke deficit during a gripping final day on the historic Old Course, with five consecutive birdies on the back nine seeing him pull clear of overnight leaders McIlroy and Viktor Hovland.
The Australian then birdied the last to close an incredible bogey-free 64, taking him to 20 under and equalling the lowest 72-hole total in men's major history, with the narrow victory his third of the season and set to lift him to world No 2.
The new Champion Golfer of the Year finished a shot clear of playing partner Young, who eagled the last to close a final-round 65, while McIlroy had to settle for third on 18 under despite a bogey-free 70.
Young responded to a close-range bogey at the first by making back-to-back birdies from the third to move to 13 under alongside Smith, who had birdied the second, as the final pairing of McIlroy and Hovland opened with three consecutive pars.
McIlroy had squandered a five-foot birdie chance at the third but moved ahead when Hovland made a three-putt bogey from 70 feet at the next, with the Northern Irishman making a two-putt birdie at the par-five fifth to double his advantage.
Young matched Smith's birdie at the fifth and two-putted for another at the seventh after driving the par-four green, lifting the American to tied-second with Hovland, only for him to follow a 10-foot par save at the eighth by bogeying the ninth after taking a penalty drop from the bushes.
McIlroy made amends from a missed birdie try at the ninth to drive the next green and almost hole his eagle putt, leaving a tap-in to move to 18 under, only to see his lead cut to one when Smith started his back nine with three consecutive birdies.
Smith added another from 20 feet at the 13th to pull level with McIlroy, who continued his run of pars, while Young birdied the same par four and Hovland nudged in from close range at the 12th to lift the pair back to within two of the lead.
Young took advantage of the par-five next to make further inroads on McIlroy, who was unable to birdie the same hole, while Smith got up and down from the back of the 14th green to register a fifth consecutive birdie and jump into the solo lead on 19 under.
Smith followed back-to-back pars by holing a clutch 12-footer to save par at the 17th, after an impressive putt around the bunker, before a stunning tee shot into the par-four last set up a two-putt birdie for victory.
Young eagled the final hole to finish a shot behind, while McIlroy was unable to find the final-hole eagle of his own to force a play-off as he ended a frustrating final day with yet another two-putt par.
McIlroy hit all greens in regulation but was left to rue a disappointing putting display, with his third-place finish extending his winless streak in majors, which stretches back to the 2014 PGA Championship.
Hovland's hopes ended when he had to come out sideways from a bunker at the 13th, resulting in a bogey, with a further dropped shot at the 16th seeing him close with a two-over 74 that dropped him to tied-fourth alongside England's Tommy Fleetwood.
Brian Harman and former world No 1 Dustin Johnson ended the week tied-sixth, while Bryson DeChambeau birdied his final three holes for a closing 66 to claim a share of eighth with Patrick Cantlay and 2017 champion Jordan Spieth.