Arsinoe of Macedon (Ancient Greek: Ἀρσινόη; lived 4th century BC) was an ancient Macedonian noblewoman and the mother of Ptolemy I Soter (323 – 283 BC), king of Ptolemaic Egypt.
Arsinoe was of the Argead dynasty, and originally a concubine of Philip II, king of Macedon, and it is said she was given by Philip to Lagus, a Macedonian nobleman, while she was pregnant with Ptolemy I Soter, but it is possible that this is a later myth fabricated to glorify the Ptolemaic Dynasty.
[1] Alternately, Ptolemy's lineage to the Argead dynasty was found through his mother, Arsinoe, in this case Arsinoe is daughter of Meleager, who was a cousin of Amyntas III and son of Balacrus, son of Amyntas, son of Alexander I of Macedon.
Contemporary and modern research concludes the latter claim much more valid than Philip II as Ptolemy’s father, now dismissed as a myth.
Dictionary of Greek and Roman Biography and Mythology.