American Collin Morikawa was on course to create history as a dramatic final round of the 149th Open unfolded at a sun-drenched Royal St George's.
Seeking to become the first player to win two different majors at their first attempt, the 2020 US PGA champion began the day a shot behind playing partner Louis Oosthuizen.
But with Oosthuizen dropping shots on the fourth and seventh, Morikawa followed six straight pars with birdies on the seventh, eighth and ninth to open up a three-shot lead over Jordan Spieth.
Oosthuizen was hoping to become the first wire-to-wire winner of the Open since Rory McIlroy in 2014, 11 years to the day since he lifted the Claret Jug at St Andrews.
The South African dropped just his fourth shot of the week after missing the green with his approach to the fourth, and then thinned his bunker shot on the par-five seventh into more sand to run up a costly six.
Spieth had fallen four shots off the pace with two early bogeys, but eagled the seventh and birdied the ninth to be out in 34, before another birdie on the 10th made him Morikawa's nearest challenger on 11 under.
Four-time major winner Brooks Koepka had set the clubhouse target on eight under following a 65, but will have been disappointed to close with six straight pars.
Former champion Rory McIlroy cut a frustrated figure after a closing 71 containing four birdies, three bogeys and a double bogey on the 10th.
The 32-year-old, who has now gone seven years since claiming his last major title at Royal Liverpool, said: "There is a lot of birdies in there but a lot of bogeys too.
"I've made 17 birdies this week, which is more than enough to challenge to win this golf tournament. It's just I make too many mistakes, and that's the part that I need to try to get right.
"There is enough good stuff in there to contend at these golf tournaments, but I'm just not allowing myself to do that with some the mistakes I'm making."