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 historic venue.
Langasque said the achievement will live long in his memory.
"I'm so happy, the last three holes were really fun and I made long putts," he said.
"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."
Countryman Frederic Lacroix was Langasque's nearest challenger on 10 under after firing a spotless 62 over at Kingsbarns, with another Frenchman - Antoine Rozner - tied for third alongside Dane Niklas Norgaard Moller on nine under.
England's Daniel Gavins was the leading British player on seven under after his bogey-free 65 at the Old Course.
World number two Rory McIlroy began the week with a 68 at Carnoustie, as did Francesco Molinari on his return to the venue where he won the 2018 Open Championship.
As well as topping the leaderboard, Langasque and partner Roy Ryu co-lead the team competition on 14 under par alongside Andrea Pavan and Kieran McManus.
Due to the weather forecast, Friday's second round will have a shotgun start at 8.30am on all three courses, with leader Langasque tackling Carnoustie on day two.