Fitzpatrick followed up his flawless round 2 with another solid outing at Le Golf National, sinking three birdies in his first six holes to get off to a flying start.
He made just one bogey and got up-and-down brilliantly to save par on the 18th to ensure he had a strong advantage going into the final day.
“I feel like I’m in a position that if I go and shoot a good round tomorrow, then obviously it makes it almost impossible to catch. But long way to go, and just take it hole by hole,” Fitzpatrick said.
Frenchman Tom Vaillant shot 67 to move into second place and will join Fitzpatrick in the final group in front of a home crowd on Sunday.
Vaillant will almost certainly add to his three top 10 finishes on the DP World Tour and will be looking to the home support to perhaps push him to a first-ever win.
“It's amazing. Whatever happens tomorrow, it’s something I will never forget — the final group here in French Open. So I’ll just try to enjoy it, and we’ll see what happens. But the main thing is enjoying tomorrow,” Vaillant said.