Jason Day's shocking last-round meltdown provided a cruel end to a horror final day for Australia's golf stars at the Masters.

From being well in contention to clinch a top-12 finish, and with it a guaranteed ticket back to Augusta National next year, Day capitulated with four double bogeys in his last 10 holes to crash to a tie for 39th.

And what spectacular doubles they were.

The first came on the par-4 ninth, when the former world No.1 four-putted after he had been hanging tough at three under par for the championship and inside the top 10.

Day stroked a brilliant, curling first putt for birdie from 44 feet to three feet, only to push his attempt for par past the hole and then also miss his try at bogey.

Seemingly rattled, Day then hooked his drive on the 10th into the trees and had to cop a penalty shot and reload en route to a second double bogey.

The car crash continued when Day, standing awkwardly inside the bunker behind the famous par-3 12th green, putted his second shot through and into the water for another double.

He had to reload again on the par-5 13th after hooking his drive deep into the Georgian pine trees.

He settled briefly with pars on 14 and 15 before dropping another shot on 16 and finishing with an elusive birdie at the last.

After adding up the damage, Day signed for an 80 and was too dejected to explain away his collapse, the soon-to-be father of five instead taking comfort with his family.

It was a depressing end to what had been another promising tournament for the resurgent star.

After top-20 finishes at all seven of his PGA Tour events in 2023, and making the quarter-finals of the WGC-Dell Technologies Match Play last time out, the former major winner arrived at Augusta as one of the outside contenders.

He lived up to that billing to be solo second at nine under par late in Friday's second round, before a watery double-bogey on the 15th precipitated his slide.

Day's stunning meltdown allowed reigning British Open champion Cameron Smith to once again finish as the leading Australian.

Runner-up at the 2020 Masters and third last year, Smith could only manage a share of 34th this campaign at four over after closing with successive rounds of 75.

"I've been on the back foot all week with the weather and wasn't particularly striking it all that well," Smith said after playing on the wrong side of the draw.

"There were lots of momentum par-saves but it was a bit of a rough week with the longer stuff."

Adam Scott also plunged down the leaderboard after the weather-hit third round resumed on Sunday.

The 2013 champion tied with Day at five over after weekend rounds of 77 and 74.

Any hopes of a final-day charge from Scott ended on round-three's 15th when he dumped two balls in the water en route to a triple-bogey eight.

Scott, though, refused to blame the draw for his lacklustre showing.