Le Mans were officially promoted to Ligue 1 on Wednesday after the French league (LFP) awarded them a 2-0 win in their interrupted final game of the season at Bastia.
The club last played in the French top flight in the 2009/10 season and were relegated to the sixth tier in 2013 for financial reasons.
They were leading Bastia 2-0 in Corsica in injury time when the referee halted the match after home fans started throwing flares onto the pitch.
Bastia were relegated to the third-tier National.
The LFP said Wednesday that Le Mans' victory was "definitively confirmed", meaning they finish the season in the second automatic promotion spot, two points clear of Saint-Etienne and seven behind champions Troyes.
Saint-Etienne will face Rodez in the play-off semi-finals on Friday.
The winners of that match will face the 16th-placed team from Ligue 1, currently Nice, later this month in the final.
Le Mans are owned by Brazilian investment fund OutField, with Real Madrid goalkeeper Thibaut Courtois, tennis star Novak Djokovic and ex-Formula One driver Felipe Massa among the minority shareholders.
