Langasque equals St Andrews record to lead Alfred Dunhill Links Championship
The Frenchman recovered from an early bogey with two eagles and eight birdies to reach 11 under par and tie Ross Fisher's record at the 'Home of Golf' in Scotland.
"I'm so happy, the last three holes were really fun and I made long putts," Langasque, 27, told the BBC.
"It's amazing. I didn't realise that I have the course record here now and I think it's something I will remember for the rest of my life."
The Dunhill Links features rounds at the nearby venues of Kingsbarns and Carnoustie as well as two at St Andrews.
A good day for French golf was enhanced by Frederic Lacroix, leading the chasing pack with a round of 62 at Kingsbarns, with yet another Frenchman - Antoine Rozner - tied for third alongside Denmark's Niklas Norgaard Moller on nine under.
World number two Rory McIlroy started the week with a 68 at Carnoustie, as did Italy's Francesco Molinari on his return to the venue where he won the 2018 British Open.
This week will see McIlroy's first appearance on the Old Course since July, when he narrowly missed out on winning the British Open.
The Northern Irishman shared the lead with Viktor Hovland heading into the final round.
But, despite shooting 70, the 2014 champion was unable to lift the Claret Jug again, with Australia's Cameron Smith coming from four strokes behind to triumph.