Marcus Kinhult made five birdies in a row on the front nine to turn in 32 and open up a five-shot lead on day three of the HNA Open de France.
The Swede entered the day two ahead but was reeled in by Spaniard Sergio Garcia after a shaky start, only to turn on the style to surge to ten under and take control of the third Rolex Series event of the season.
Garcia and countryman Pedro Oriol were part of the chasing pack along with Swede Alexander Björk and England's Chris Wood.
World Number Two Justin Thomas and fellow American Julian Suri were at four under alongside Spaniard Jon Rahm, with Swede Alex Noren and Spain's Adrian Oteagui in the clubhouse seven shots off the lead.
Kinhult graduated from the Qualifying School in 2015 but made just two cuts in his debut campaign, switching to the Challenge Tour and earning a second European Tour season via the Road to Oman in 2017.
After finishing third at the Commercial Bank Qatar Masters in February, he has made just three of eight cuts since, although one of those was a tie for 12th at the BMW PGA Championship.
Noren made fast progress through the field with birdies on the first, third, sixth, seventh, tenth and 13th and, when he took advantage of the par five 14th from five feet, he was in a share of second.
He found the water on the next to drop a first shot of the day but parred his way home to set the target at three under.
Garcia had gains on the first, third and driveable sixth and when he made a stunning up-and-down on the ninth, he was one shot off the lead.
Kinhult chipped in on the first to get to seven under and bring a fist-pumping celebration but a double-bogey on the next after finding water off the tee brought him back to the pack.
He made a wonderful up-and-down of his own from the hay on the fourth but that did not keep him in the lead as Garcia put his tee-shot on the 11th to tap-in range to join him.
Parity would not last for long, however, with Kinhult holing a long putt on the fifth to get back to where he had started the day at six under.
He took the rare decision to lay-up on the sixth but easily made his birdie before putting an approach inside six feet on the next to lead by three.
A stunning tee-shot on the eighth to five feet made it four in a row and when the 21 year old laid-up and played the ninth in textbook fashion, he was ten under and five ahead.
Oriol made birdies on the fourth, fifth eighth and ninth, while Björk made a hat-trick of gains from the 12th after turning in 34.
Wood was three over for his round after five holes but birdied the sixth and eighth before chipping in for an eagle at the par five ninth.
Suri had gains on the third and sixth, Thomas turned in 34 after a roller coaster start, and Rahm made three birdies to recover from a double on the third.
Otaegui made six birdies and a bogey in his 66.
