Angel Cabrera posted a 6-under 66 to move to 11-under-par 205. He shares second place with Jarmo Sandelin (67), Mark McNulty (68), Alastair Forsyth (69) and local favorite Darren Clarke (70).
Price and Clarke began the day tied for the lead on the North Course at The Kildare Hotel & Country Club. Price however took control right away. He birdied each of the first two holes to grab the advantage.
The Welshman's lead remained two after a birdie at the fourth got him to 12- under. Clarke birdied the same hole and Forsyth birdied No. 5 to move to minus-10. Forsyth quickly fell off the pace with back-to-back bogeys from the sixth.
Price's lead stretched to three when he ran home a birdie putt at the seventh. The momentum shifted when Price bogeyed the eighth and Clarke birdied No. 10 to get within one shot.
Price, the 2002 Ryder Cup hero for the European squad, regained the momentum with a birdie at the 12th to grab a two-stroke lead over Clarke. He then birdied the 15th to extend his lead to three.
The two-time Open de Portugal winner made it two straight with a birdie on the 16th to get to 15-under and stretch the advantage to four strokes.
Price's lead dropped to three when he bogeyed the 17th after his drive found the right rough. He tried to punch a shot down the fairway, but hooked it into a hazard. He played from within the hazard, but could not get the ball to the green with his third shot. He pitched on with his fourth and saved bogey from there.
He could have extended his lead back to four but his birdie try on the 18th came up short left. Clarke also missed his birdie attempt at the last.
'I am hoping I can draw on the Ryder Cup experience,' said Price. 'I am going to feel pretty much as I did that day and I hope I can deal with it exactly the same way that I did then.
'I will get butterflies but once you settle down you're away. I suppose I learned that you can still play feeling nervous. I was very determined that day against (Phil) Mickelson and I'm going to be doing the same thing tomorrow.'
Clarke managed just those two birdies en route to a 2-under 70.
'Someone will have to play very well to win,' Clarke said. 'Phillip played really nicely. He shot 67 but it could quite easily have been 63. He hit it that close, so someone will have to play very well to beat him.'
Cabrera started his day four shots back and did not get going until late on the front nine. He bogeyed the sixth to drop another shot off the pace but quickly responded. He notched back-to-back birdies from the eighth, then ran off three consecutive birdies from the 11th.
Down the stretch, Cabrera birdied the 16th and 18th to grab a share of second.
Forsyth had a pair of birdies and bogeys over his first seven holes. He birdied the eighth but stumbled to another bogey at the 10th. He moved back into contention with birdies at Nos. 13, 16 and 18.
Sandelin opened with two straight bogeys but erased those mistakes with an eagle at the par-5 fourth. He notched a pair of birdies at the eighth and 10th, but dropped a shot with a bogey in No. 11. From there, he posted four birdies, including back-to-back from the 17th to close his round.
McNulty started slowly with just one birdie over his first 10 holes. He posted two straight birdies from the 11th, but bogeyed the 13th. He came right back to birdie the 14th and later the 16th for a share of second place.
Andrew Coltart and Gary Evans share seventh place at 9-under-par 207. Eduardo Romero, Klas Eriksson and Retief Goosen are tied one stroke further back at minus-8.
Colin Montgomerie managed just a 1-over 73 to fall to 4-under and a tie for 20th. He did however produce the highlight of the day with his eighth career hole-in-one on tour, this one coming at the par-3 12th. It was the 12th ace on the European Tour this season.
Michael Campbell, the 2002 champion, made a small move to 1-under-par 215 after a third-round, 2-under 70.