Ptolemaeus (Ancient Greek: Πτολεμαῖος, romanized: Ptolemaios) or Ptolemy (died 309 BC) was a nephew and general of Antigonus I Monophthalmus, one of the Successors of Alexander the Great.
In 315 BC, when Antigonus moved against the coalition of Diadochi formed against him, he placed Ptolemy at the head of an army which marched against the generals of Cassander in Asia Minor.
The young general successfully carried out his mission, relieving Amisus, which was besieged by Asclepiodorus, and recovered the whole satrapy of Cappadocia; after which he advanced into Bithynia, compelling king Zipoites to join Antigonus.
Calling all his forces from their winter quarters, he divided them into four columns: the first was sent to take Miletus; the second under Ptolemy through central Caria from east to west; a third to take Theangela; and Antigonus himself with the main army campaigned from north to south capturing Tralles, Iasus and Kaunos.
The next year Ptolemy was sent with a considerable army and fleet to take over from Telesphoros; Antigonus made him commander in chief of all his forces and affairs in Greece.
[5] His successes were at first rapid: he drove out the garrisons of his adversary from Chalcis and Oropus, invaded Attica, where he compelled Athens's tyrant Demetrius Phalereus to make overtures of submission, and then carried his arms triumphantly through Boeotia, Phocis, and Locris.
He was received at first with the utmost favour, but soon gave offence to his new patron by his intrigues and ambitious demonstrations, and was in consequence thrown into prison and compelled to commit suicide by poison in 309 BC.