Ghilas, 28, spent a successful loan spell at Reims as they gained promotion from Ligue 2.
And he will link up with them again in the top flight, penning a two-year contract, the club announced in their website.
Ghilas scored 14 goals last season, making him the second-top scorer in Ligue 2.
He spent past of the 2010-11 season on loan at Arles-Avignon in Ligue 1. They were relegated but he did score twice in 19 matches.