After the death of Alexander in 323 BC, Ptolemy retrieved his body as it was en route to be buried in Macedon, placing it in Memphis instead, where it was later moved to Alexandria in a new tomb.

After a series of wars between Alexander's successors, Ptolemy gained a claim to Judea in southern Syria, which was disputed with the Seleucid king Seleucus I.

He later married Eurydice, daughter of the Macedonian regent Antipater; their sons Ptolemy Keraunos and Meleager ruled in turn as kings of Macedon.

According to Satyrus the Peripatetic, Arsinoe was a descendant of Alexander I of Macedon and thus a member of the Argead dynasty, claiming ultimate descent from Heracles.

Ostensibly, Ptolemy's father was Lagus, a Macedonian nobleman from Eordaea, but many ancient sources claim that he was actually an illegitimate son of Philip II of Macedon.

On his deathbed, Alexander wished to be buried at the Temple of Zeus Ammon in the Siwa Oasis of ancient Libya instead of the royal tombs of Aigai in Macedon.

He brought Alexander's remains back to Egypt, interring them at Memphis, but they were later moved to Alexandria where a tomb was constructed for them.

[16] Ptolemy was consistent in his policy of securing a power base, while never succumbing to the temptation of risking all to succeed Alexander.

When Antigonus I, master of Asia in 315, showed expansionist ambitions, Ptolemy joined the coalition against him, and on the outbreak of war, evacuated Syria.

[9] In 312, Ptolemy and Seleucus, the fugitive satrap of Babylonia, both invaded Syria, and defeated Demetrius I, the son of Antigonus, in the Battle of Gaza.

Soon after this, the surviving 13-year-old king, Alexander IV, was murdered in Macedonia on the orders of Cassander, leaving the satrap of Egypt absolutely his own master.

[18] In 309 Ptolemy personally commanded a fleet which detached the coastal towns of Phaselis, Xanthos, Kaunos, Iasos and Myndus in Lycia and Caria from Antigonus, then crossed into Greece, where he took possession of Corinth, Sicyon and Megara (308 BC).

In 306, a great fleet under Demetrius attacked Cyprus, and Ptolemy's brother Menelaus was defeated and captured in another decisive Battle of Salamis.

[9] The satraps Antigonus and Demetrius now each assumed the title of king; Ptolemy, as well as Cassander, Lysimachus and Seleucus I Nicator, responded by doing the same.

In the winter of 306 BC, Antigonus tried to follow up his victory in Cyprus by invading Egypt; but Ptolemy was strongest there, and successfully held the frontier against him.

But when the news came that Antigonus had been defeated and slain by Lysimachus and Seleucus at the Battle of Ipsus in 301, he occupied Syria a fourth time.

[19] While Alexander was alive, Ptolemy had three children with his mistress Thaïs, who may also have been his wife: Lagus; Leontiscus; and Eirene, who was given in marriage to Eunostos of Soloi in Cyprus.

His reputation for good nature and liberality attached the floating soldier-class of Macedonians and other Greeks to his service, and was not insignificant; nor did he wholly neglect conciliation of the natives.

[34] For example, Arrian's account of the fall of Thebes in 335 BC (Anabasis 1.8.1–1.8.8, a rare section of narrative explicitly attributed to Ptolemy by Arrian) shows several significant variations from the parallel account preserved in Diodorus Siculus (17.11–12), most notably in attributing a distinctly unheroic role in proceedings to Perdiccas.