Ptolemy I (Ptolemy Soter)tŏl´əmē sō´tər [key], d. 284 BC, king of ancient Egypt, the first ruler of the Macedonian dynasty (or Lagid dynasty), son of a Macedonian named Lagus. He was one of the leading generals of Alexander the Great, and after Alexander's death (323 BC) he joined the other Diadochi in dividing and quarreling over the empire. Ptolemy received Egypt and managed to keep control of it in the midst of incessant warfare. To strengthen his position he married Eurydice, daughter of Antipater (though he soon shifted his affection to her niece and his own half-sister, Berenice). He defeated (321) Perdiccas, and he at first supported Antigonus I in the confused struggle for imperial power. He defeated Eumenes, then fearing Antigonus' efforts to remake the empire, allied himself with Cassander and Lysimachus. Ptolemy defeated the troops of Antigonus in 312 but he was defeated at Salamis in 306, and the ultimate defeat and death of Antigonus at Ipsus in 301 resolved the situation. Ptolemy had already declared himself king in 305. Subsequently he laid the outline for Ptolemaic administration in Egypt and did much to make Alexandria a fountainhead of culture and art by founding the library there. Through Arrian, we know that he wrote a history of Alexander.
See J. P. Mahaffy, The Empire of the Ptolemies (1895); E. R. Bevan, A History of Egypt under the Ptolemaic Dynasty (1927); P. M. Fraser, Ptomemaic Alexandria (3 vol., 1972, repr. 1984).
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