Xander Schauffele posted a flawless 64 on the opening day of the JP McManus Pro-Am to establish a commanding three-shot lead at the halfway stage.
The American Ryder Cup star fired eight birdies - including three in a row towards the end of his round - and no bogeys at Adare Manor Hotel & Golf Resort to get to eight under par and give himself a huge advantage in the 36-hole event.
A world-class field has gathered at Adare Manor for the sold-out Pro-Am, and some of the game's very best players are waiting to hunt down Schauffele on Tuesday.
Fellow American Rickie Fowler is Schauffele's nearest challenger on five under after making an eagle at the 15th on his way to a first-round 67.
Six-time DP World Tour winner Tyrrell Hatton was alone in third a shot further back after carding an eagle and two birdies in his last four holes.
Home favourites Seamus Power and Shane Lowry, two of the star attractions in County Limerick, were among those on three under.
Rory McIlroy, Tiger Woods and a host of big-name celebrities also drew huge crowds on day one.
Starting from the tenth tee on Monday, Schauffele made back-to-back birdies at the 12th and 13th before taking advantage of the par-five 18th to turn in 33.
After picking up further shots at the first and third, Schauffele pulled clear of the field with a hat-trick of birdies from the fifth to jump to eight under.
And he closed his first round with pars at the eighth and ninth to head into Tuesday's second and final round with a three-stroke cushion.
The Gerry McManus Team, who played with McIlroy on Monday, lead the team event on 22 under par.