Best four-ball ever for Horan
The world number one has teamed up with the 21-year-old singer from County Westmeath - who makes his debut at the event after he caddied for four-time major winner McIlroy in the pre-Masters tournament at Augusta National last month - along with former England internationals Phil Neville and Paul Scholes.
The annual curtain-raiser to the BMW PGA Championship gets under way on May 20 at Wentworth's iconic West Course and the quartet are due to tee off at 8am.
Horan, who is listed as an honorary life member of Mullingar Golf Club in Ireland, is used to performing in front of large crowds with One Direction, but admitted he hoped the nerves would not get the better of him when playing at Wentworth.
He said: "I can't wait to play with Rory, Phil and Paul. It's going to be a great event. I know how prestigious the BMW PGA Championship is as the European Tour's flagship event, so the opportunity to play in the Pro-Am with my mate Rory and two legends of football is going to be amazing - what a team!
"That said, I've heard there are pretty big crowds there on the day, I'm used to those but not when I'm on a golf course. I'll probably be more nervous at Wentworth than I was performing in front of thousands with 1D, so I'm hoping Rory will give me a few tips on calming the nerves."
McIlroy added: "Niall and I had a good fun together in the Par 3 contest at the Masters and I'm looking forward to seeing him again at Wentworth. It should be a great four-ball with Phil and Paul playing too, and it should appeal to a wide range of fans.
"The Celebrity Pro-Am is always one of the most enjoyable days of the year and I'm sure the guys will all have a great time."