Lowry carded seven birdies and three bogeys in an opening 68 to trail clubhouse leader Shubhankar Sharma by three shots on a sweltering opening day at The K Club.
The former Open champion, who was still an amateur when he won the Irish Open in 2009, will defend his BMW PGA Championship title next week and then make his second appearance in the Ryder Cup at the end of September, with Europe seeking to regain the trophy in Rome.
“Take away everything else that’s in the next few weeks, this is a big week for me, ” Lowry said. “I want to go out there and play well and give myself a chance to win this tournament.
“It’s only 45 minutes to an hour from where I’m from in Clara. I want the people to be getting on their buses on Sunday morning to come and watch me try and win this tournament.
“That’s all I want this week. It’s nothing to do with the Ryder Cup or Wentworth next week or anything.
“This tournament for me is huge. I feel at home here. I live in Florida and I miss home a lot when I’m away. It’s nice to be back.”
Lowry’s 68 was matched by compatriot Mark Power, who carded two birdies and an eagle on the 18th in his first start as a professional, as well as Ryder Cup captain Luke Donald, while Rory McIlroy returned a 69.
McIlroy, who won the tournament the last time it was staged at The K Club in 2016, started on the back nine and bogeyed his first hole following a wayward drive and penalty drop, but birdied his last two holes to end the day on a high.
“I think the two birdies in the last two holes sort of glossed over what was a pretty average day,” McIlroy said. “Didn’t really feel great with anything.
“It’s hard to say I’m rusty when I’ve only had a week off but I just haven’t had a chance to practice much and I just hit a few loose shots out there.
“Managed my game well and scraped it around in three under which is nice and sort of gets me in the tournament.
“I’m hitting good shots but it’s all about knowing your patterns and where you’re missing it and where to aim and where not to aim and just being a little unsure over a couple of shots.”
Sharma’s flawless 65 gave him a one-shot lead over Jordan Smith, Ross Fisher, Marcel Schneider, Kristian Johannessen and Ryder Cup vice-captain Thomas Bjorn.
Defending champion Adrian Meronk, who admitted on Wednesday he was shocked and angry to be overlooked for a Ryder Cup wild card, matched the 69 of playing partner McIlroy, with the third member of the group, American Billy Horschel, also carding the same score.