Lille land former Chelsea forward Kalou
The former Chelsea attacking midfielder has penned a four-year deal, the French club said in a statement.
Kalou, 26, had mostly been a bit-part player during his six years with the London club and was released after his last appearance in the Champions League final win over Bayern Munich in May.
The arrival at Stamford Bridge of Belgium wingers Hazard and Kevin de Bruyne, as well as German Marko Marin, had made Kalou's departure from Chelsea inevitable.
Lille, Ligue 1 champions in 2011 before finishing third last term, have also lost loan winger Joe Cole who has returned to his parent club Liverpool.