McIlroy, who won the Open Championship Sunday by two shots over Rickie Fowler and Sergio Garcia, opened as a 7/1 favorite for the season's final major at the LVH Superbook in Las Vegas. Adam Scott was next at 12/1, followed by Tiger Woods at 15/1 and Phil Mickelson at 20/1.
A large group of golfers at 25/1 includes Fowler, Garcia, Dustin Johnson, Matt Kuchar, Jason Day, Henrik Stenson, Martin Kaymer, Jordan Spieth and Justin Rose. Masters champ Bubba Watson is listed at 30/1 alongside the top two names on last year's PGA Championship leaderboard, Jason Dufner and Jim Furyk.
In addition to cashing in for his father with his win at Royal Liverpool, McIlroy rewarded his backers handsomely after beginning the week in Hoylake at 15/1 odds in Las Vegas, listed behind Scott and Rose who were co-favorites at 12/1. McIlroy's odds were trimmed to 4/1 after his opening-round 66, and by the time he teed off Sunday with a six-shot lead, he was a whopping 1/10 favorite to win the Open.
While he was only 11 years old the last time the event was staged at Valhalla in 2000 and did not participate in the 2008 Ryder Cup held there, McIlroy does boast a strong record in the PGA Championship, with four top-eight finishes in five career appearances highlighted by his eight-shot romp at Kiawah Island in 2012.
McIlroy is expected to tee it up at next week's WGC-Bridgestone Invitational, with the PGA Championship held the following week in Louisville, Ky.