Wicklow's Paul Dunne carded a three-under-par 68 to lead the field by one shot ahead of the final round of the Open de Espana.
Dunne, who began the day three strokes clear, registered five birdies and a bogey to reach 17-under-par but Spaniard Nacho Elvira stayed in contention with seven gains and two dropped shots in his third round.
World number four Jon Rahm and Sweden's Henric Sturehed finished on 15 under after both players recorded six-under 66 cards, with Australia's Brett Rumford a shot further adrift in fifth and England's Andy Sullivan sitting in sixth.
Dunne opened up with four pars before a hat-trick of birdies from the fifth moved him two clear of Spaniard Rahm and Sturehed and a gain at the 12th put the Irishman further ahead.
He handed that stroke back at the penultimate hole to remain at 16 under but the 25-year-old finished with a flourish with his fifth birdie to remain on course for his second European Tour title.
"It's probably the best my swing has felt, the best my body has felt like it's been moving, but I just didn't pull the shots off," Dunne told Sky Sports.
"There was a lot of grinding there on the back nine but I'm happy to get in with four under.
"I probably wouldn't have taken it at the start of the day but, given the shots that I hit, I'm pretty happy with it leading into tomorrow.
"I'm confident about tomorrow. There's lots of shots I'd like to have back out there but I can't so I'm just going to sleep on the lead and have a good day tomorrow.
"Hopefully it gives me a chance to win and we'll see where it takes us."
Home favourite Rahm turned in for 33 after birdies on the first, second and sixth before picking up two more shots at the 10th and 11th.
A bogey at the 14th blotted his scorecard but he responded by carding birdies at the 15th and the last to put him in serious contention at the Centro Nacional de Golf.
Englishman Sullivan carded the round of the day with eight gains and just one dropped shot to support his stunning second round of 63.