But Masters and US Open champion Jordan Spieth is just a shot behind the leading trio of Dunne, Louis Oosthuizen and Jason Day as he looks to claim the third leg of an unprecedented calendar Grand Slam at St Andrews.
University of Alabama student Dunne, 22, is the first amateur since Bobby Jones to lead the Open after 54 holes, the American going on to lift the Claret Jug at St Andrews in 1927.
Three years later, Jones became the last amateur winner of the Open to date at Royal Liverpool and went on to complete the ‘Impregnable Quadrilateral’ of Amateur Championship, Open Championship, US Open and US Amateur titles.
As an amateur, Dunne cannot collect the record ??1,150,000 first prize if he wins, but would get to lift the Claret Jug as Open champion as well as the silver medal awarded to the leading amateur.
“I don’t see why not,” said Dunne, who at 12 under par was three shots ahead of American amateur rival Jordan Niebrugge.
“I’m well capable of shooting the scores that I need to win if everyone else doesn’t play their best.
“Whether it happens or not, I can’t really control. I can just go out and try to play my game and see where it leaves me at the end of the day.
“It’s surreal I’m leading the Open, but I can easily believe that I shot the three scores that I shot.
“If we were playing an amateur event here, I wouldn’t be too surprised by the scores I shot. It’s just lucky that it happens to be in the biggest event in the world!”
Spieth is looking to become the first player to win the first three majors of the year and just the third to win any three in a single season – Ben Hogan won the Masters and US Open in 1953 but missed the US PGA to compete in, and win, the following week’s Open at Carnoustie, while Tiger Woods won the US Open, Open and US PGA in 2000 and completed the ‘Tiger Slam’ in the 2001 Masters.
“It hasn’t come up in my head while I’ve been playing yet,” said the 21-year-old, who would also replace Rory McIlroy as world No 1 with victory.
“If I have a chance coming down the stretch, if it creeps in, I’ll embrace it. I’ll embrace the opportunity that presents itself.
“I don’t look at it as a negative thing, I look at it almost as an advantage. Why should it add more pressure in a negative way?
“If it adds more pressure, it just makes me feel like this is something that’s a little more special, let’s go ahead and get the job done.”
Two-time Open champion Padraig Harrington was two shots off the lead, with Sergio Garcia, Justin Rose, Adam Scott and Danny Willett among a nine-way tie for sixth on nine under.