Ptolemaida is a town and a former municipality in Kozani regional unit, West Macedonia, Greece. Since the 2011 local government reform it is part of the municipality Eordaia, of which it is the seat and a municipal unit. It is known for its coal (lignite) mines and its power stations.
During the Ottoman period, the city was named Kaylar, rendered into English as Kailar; this name was retained in Greek as Kailaria until 1927 Kailar refers to the Kayı tribe, the tribe of Osman I, the founder of the Ottoman Empire. The modern name Ptolemaida was introduced by decree on January 20, 1927, honoring Ptolemy son of Lagus, a comrade-in-arms of Alexander the Great, and his daughter Ptolemaïs. His statue stands in the central square of the city.
Archaeologists, in November 2005, discovered the remains of two farming villages dating back to the Neolithic period. A press report notes that such farming villages were trading centres and had a "developed knowledge of metalworking".