McIlroy's bogey-free round of 66 couldn't be matched and the world number 8 sits a shot clear of the field on 6-under par.
Italy's Matteo Manassero is a shot back on 5-under.
Shane Lowry is in a group of 7 players that are tied for third place on 4-under par after a superb back-nine performance from Lowry that took him just 32 shots including a birdie on the 18th.
Of the rest of the Irish players...
- Earlier, 2011 champion Darren Clarke finished the day on level par
- Graeme McDowell and Padraig Harrington both finished on 2-over
- Michael Hoey and amateur player Paul Dunne both had to settle for 3-over par rounds of 75