Ptolemaïs (ptôlĬmīs´), town (1991 pop. 25,195), N Greece, in Macedonia. It was a small market town until 1958, when it began to be developed as an industrial center. Lignite, mined there in vast quantities, is used to power thermoelectric plants, which produce electricity for iron and steel mills, aluminum factories, and chemical plants. New dams in the area provide additional hydroelectric power.

Ptolemaïs (tŏləmā´īs), ancient name given to several cities to honor members of the dynasty of the Ptolemies. One of these later became known as Akko, in modern Israel. Another was one of the great Hellenistic cities of Upper Egypt, on the Nile and N of Abydos. A third, in Cyrenaica, was one of the cities of the Libyan Pentapolis.