Nice have parted ways with coach Patrick Vieira following a poor run in the French Ligue 1.
The former Arsenal star leaves the club after two-and-a-half years in charge on his three-year contract, which was to end next year.
In a statement, Nice wrote: "During an interview after last night's meeting, the Nice board informed Patrick Vieira of its decision to end their collaboration.
"The management of the red and black club made the decision to entrust Adrien Ursea with the mission of leading the professional team from today.
"The Swiss-Romanian technician, until now assistant coach of Patrick Vieira after being that of Lucien Favre will make his first match on the Nice bench as head coach during the trip to Reims this Sunday.
"Patrick Vieira will have put all his heart and his professionalism at the service of OGC Nice during the 30 months that this common adventure will have lasted.
"The Nice managers would like to sincerely thank the former French international for his involvement in the development of the Club and wish him the best for the rest of his coaching career."
Results have not been coming for the 44-year-old, with Nice losing five in a row in all competitions.
The latest two losses came on Sunday night when they lost 3-1 at home against Dijon, which was quickly followed by a 3-2 humbling by Borussia Monchengladbach in the Europa League on Thursday night.