Bernd Wiesberger carded a flawless 6-under 65 on Saturday and leads the Portugal Masters by one shot heading into the final round.
Wiesberger had six birdies in a seven-hole stretch beginning on No. 8. England's Ross Fisher, who was in the lead at the start of the third round, shot a 2-under 69 and is right behind the Austrian.
The 27-year-old Wiesberger will try to close out his third European Tour win of the season on Sunday at the Oceanico Victoria Golf Course. He's at 13-under 200 for the tournament.
"I played beautifully on the back nine," he said. "After seven holes I was not thinking about a 65. I had some horrible wedges early on but I grinded through that and hit better shots around the turn."
Ireland's Shane Lowry (67), England's Richard Finch (66) and New Zealand's Michael Campbell (67) are tied for third, four strokes back of the leader.
Fisher played through pain from a strained ligament in his left foot that he injured early on Friday.
"It was heavily bandaged and I tried to take the weight off it as much as I could," Fisher said. "It's quite bruised, but the swelling is not as bad as I was told it might be.
"I'm disappointed to drop a shot on the last. I tried to keep my neck out in front, but there's still a lot of golf to play."
Spanish veteran Miguel Angel Jimenez (68) and England's Mark Foster (67) are tied for sixth at 205.