Rory McIlroy's Open Championship hopes are in tatters after a first-round horror show at Royal Portrush ended with the home favourite carding an eight-over-par 79.

All eyes were on McIlroy as The Open returned to Northern Ireland for the first time in 68 years, but his hopes all but disappeared with a sickening quadruple bogey at the first hole.

The four-times major champion ended his day not only looking up at a leaderboard headed by American JB Holmes, but knowing he will need a stellar second round merely to make the halfway cut.

Ireland's Shane Lowry was the clubhouse leader for a couple of hours after a four-under-par 67 on a day of wind and squally showers, mixed with dazzling sunshine.

"I took my chances when I got them early on," said Lowry.

"At the start of my back nine, I missed a few chances. But look, I think four-under is a great score on that course and I'll take it any day."

His score was later overtaken by Holmes.

A large group two back included world number one Brooks Koepka, who made an ominously good start with a tidy performance that was bogey-free until a wayward drive at the 17th.

Koepka, seeking to complete one of the greatest major championship years after going second, first and second at the Masters, PGA Championship and US Open, was guided around Portrush by caddie Ricky Elliott, who hails from the area.

"He just tells me where to hit it and I go from there," Koepka said of Elliott.

"The game plan's pretty concrete. It's actually quite easy. I really don't have to do much thinking. I just go out there and play."

Other leading names did not enjoy their best opening rounds at the last major of the year.

Defending champion Francesco Molinari of Italy struggled to a three-over 74, former winner Phil Mickelson shot 76 and Masters champion Tiger Woods, among the late starters, was six over par after 16 holes.

McIlroy once scored 61 around Portrush as a teenager but began his challenge for the Claret Jug he won in 2014 like a Sunday morning amateur.

He was cheered to the first tee but those cheers quickly turned to groans.

McIlroy's opening tee shot went out of bounds, breaking a spectator's phone in the process. His follow-up found heavy rough and from there he struck his next shot into an unplayable lie in a bramble bush.

After taking a penalty drop, McIlroy chipped on to the green and two-putted. He picked his ball out of the hole, to sympathetic applause, with an ugly eight on his card.

The 30-year-old bogeyed the par-three third and although he repaired some of the damage with birdies at seven and nine, the gremlins returned. He double-bogeyed the par-three 16th and triple-bogeyed the last before trudging off.

Earlier, Graeme McDowell drew loud cheers from the packed galleries as he got to three under after 14 holes on his hometown course but he leaked five shots in the last four holes.

McDowell played the first 14 holes in three under par but then three-putted the 15th and 17th and ran up a triple-bogey seven on the 18th after losing his ball following a wayward drive.

The former US Open champion's ball was found just seconds after his allotted search time had expired, that time having been reduced from five minutes to three minutes in January this year.

"I thought it was a hell of a rule there until about 12 minutes ago," McDowell said with a wry smile after signing for an opening 73.

"It's amazing, five minutes feels like a long time when you're looking for a ball. And three minutes feels like no time at all. We had 30 people over there looking for that thing. Twelve seconds after the three minutes was up we found it.

"Unfortunately it was 10 yards right of where I thought it was. For some reason no-one saw it and the marshals didn't get an eye on it.

The 148th Open began with McDowell's compatriot Darren Clarke striking the first tee shot on an historic morning on the Antrim coast. Clarke made three birdies in his first five holes before carding level-par 71
One of the biggest roars greeted Emiliano Grillo's hole-in-one on the par-three 13th. The 26-year-old Argentine's ace was the first at The Open since Louis Oosthuizen in 2016.

Despite damp weather for a second successive day, fans arrived early and in number for the sold-out tournament, with the expected total attendance of 237,750 making it the best attended Open outside of St Andrews in Scotland.