The 58 year-old has been handed a deal that runs through until 2021 and succeeds Jean-Louis Gasset, who he worked under as an assistant last season.
Gasset had been in charge of Saint-Etienne since December 2017 but he stepped down after guiding his side to a fourth-place finish in Ligue 1.
Saint-Etienne opted for continuity by promoting Printant, and the former Bastia boss is ready for the challenge ahead as the Stade Geoffroy-Guichard gears up for the return of European football.
"I feel a great sense of pride and I thank the leaders for their trust," he told the club's official website. "I have the ambition and energy to continue all the work put in place for 18 months with Jean-Louis Gasset.
"Saint-Etienne is one of the biggest French clubs and we have succeeded in moving the club back to its level from a lot of work on and off the pitch.
"I hope to meet the expectations of my bosses and the supporters, and I will do everything I can to relive exceptional moments like those we experienced a few weeks ago by qualifying for the Europa League in front of our wonderful fans."