Lille can relinquish top spot to Saint-Etienne or Rennes if either wins when they meet on Saturday. They are one point behind Lille.
The 35-year-old Yılmaz netted 229 goals during a long career in Turkish soccer in which he starred for Istanbul-based Galatasaray, but had not scored in his first four games for Lille.
He ended that lean spell from a penalty in the 87th minute, earning it himself with a neat turn that drew a foul from defender Dennis Appiah.
Yilmaz's countryman, Zeki Çelik, played a part in the opening goal when, moments before halftime, the right back's cross led to an own goal from center half Nicolas Pallois.
In Saturday's other game, Marseille hosts struggling Metz at Stade Velodrome.
