Adam Scott leads Australians at Open Championship, Cameron ...

Cameron Smith, who won the Open Championship in 2022, shot an opening round nine-over 80, ending his hopes of a second Claret Jug.

Adam Scott was the only Australian under par in the opening round at Royal Troon.

The second round of the Open Championship begins on Friday afternoon, AEST.

Adam Scott and Min Woo Lee have risen before first light to illuminate Australia's British Open chances — but Cameron Smith's hopes of reclaiming his 2022 title were plunged into darkness after a horror opening round at Royal Troon.

Scott and Lee might not have been too thrilled to trudge out of bed in the dead of night to prepare for yawningly early tee times on Thursday, but both made the best of damp, squally conditions that only really improved late in the day as Irishman Shane Lowry grabbed the outright lead with a five-under 66.

Scott, who began with splashing in a birdie straight from the bunker at 7:40am local time, shot a one-under 70, just a stroke better than Lee, who recorded three birdies in his last four holes to get to level par, both right in the thick of the battle.

Lee was the first Aussie out at 7:19am, which meant the Perth ace was up at 4am to prepare after a restless night.

An unsurprisingly sluggish start followed as the 25-year-old bogeyed two of the first three holes, suffered a double bogey after driving out of bounds at the 11th "Railway" hole, but finished like a champ, with birdies from 14ft at 15, 8ft at 16, and 10ft at the last.

In the group behind, Scott, two days after his 44th birthday, opened his 24th successive Open bid with his spectacular splash-in, feeling it was the launch-pad for a "very solid" round which persuaded the 2013 Master he could again contend for the Claret Jug after three previous top-five finishes.

"My game is finally in some decent shape where I feel like I'm controlling the ball well," Scott said.

Meanwhile, Smith's chances of a second Claret Jug are over.

Nothing went right from the start as the Queenslander found thick rough with his opening drive that led to a bogey, then ended up with a seven at the second after driving out of bounds.

Completely out of sorts playing alongside leader Lowry, the 30-year-old, coming off three top-10 finishes in his last four LIV Golf Tour events, recorded nine bogeys alongside his triple, but at least showed champion's spirit by birdieing two of the final three holes.

"Just a bad day, really. I mean, if you had have told me yesterday that I was going to shoot that, I wouldn't have said that was possible," shrugged Smith, whose 80 matched that of Australia's amateur debutant Jasper Stubbs, who qualified by winning the Asia-Pacific Championship at Royal Melbourne near his home.

Jason Day, the top-ranked Aussie who finished runner-up last year, ended with a 73 which he called "a decent start".

"I've just got to kind of clean up the mistakes a little bit and get myself back in the tournament," Day said.

Elvis Smylie, the 22-year-old son of former Aussie tennis star Liz Smylie, launched his major debut with a five-over 76.

AAP