Ptolemy I (367?-283? bc), called Ptolemy Soter (“preserver”), ruler of Egypt (323-285 bc), founder of the Ptolemaic dynasty. The son of Lagus, a Macedonian of common birth, Ptolemy was a general in the army of Alexander the Great and took a leading part in Alexander's later campaigns in Asia. On the death of Alexander in 323 bc, his empire was divided among the Diadochi (successors) by the imperial regent Perdiccas and Ptolemy was appointed satrap of Egypt and Libya. He was from the first an independent ruler, engaging in long wars with other Macedonian chiefs in order to secure and extend his rule. Ptolemy was prevented from holding Cyprus and parts of Greece, but he resisted invasions of Egypt and Rhodes and occupied Palestine and Cyrenaica. In 305 bc he assumed the title of king. Alexandria was his capital, and he founded the famous Alexandrian library (see Alexandria, Library of). He was the author of a lost history of the campaigns of Alexander. In 285 bc Ptolemy I abdicated in favor of one of his younger sons.