Four-time major winner Rory McIlroy leads by two strokes after a first-round 65 that included an eagle at the Arnold Palmer Invitational at Bay Hill in Florida on Thursday.

McIlroy made six birdies and an eagle on the 16th hole to card a seven-under-65 with a bogey on the 11th the only blemish on his scorecard.

The Northern Irishman, who made 11 of 14 fairways, leads by two strokes from American trio Beau Hossler, JJ Spaun and Billy Horschel, with a group of six players one further shot back including Sungjae Im and Will Zalatoris.

“This is my fourth start of the calendar year. I’ve had one really good chance to win and probably one other half chance," McIlroy told reporters after day one.

"I feel like I’m playing well enough to have chances to win golf tournaments, but all you can ask of yourself is to keep putting yourself in those positions on Sundays and then you see where your game really is.

“Hopefully, this is another week where I put myself in a position where I can really see where my game is when the pressure is on.”

McIlroy's day was highlighted by his 41-foot putt for eagle on the par-five 16th hole.

"I played the par-fives particularly well, and that was the bulk of the score," said McIlroy who won at Bay Hill in 2018.

"I've said this all along: You can play within yourself here and still shoot a good score, I feel, if you're just disciplined and pick off the birdies where you're supposed to."

McIlroy is one of four players from the PGA Tour's top six, with world number one Jon Rahm struggling with an even round on the opening day - including falling short on a gimme putt - to be seven shots off the pace.

Viktor Hovland carded a three-under-round of 69, while Scottie Scheffler is two under after the first day.