Ptolemais (Ancient Greek: Πτολεμαΐς) was a tribe (phyle) added by the ancient Athenians to the previous list of 12 Athenian tribes. The date of the addition used to be subject of a scholarly discourse, but modern researchers agree with William Scott Ferguson who (in 1932) suggested that the event took place in 224–223 B.C. Ptolemy III was chosen as one of the Eponymous Heroes due to urgency of keeping friendship with Ptolemaic Egypt. The Monument of the Eponymous Heroes had one statue added, starting the so-called Period III.
While the Athenians added the new phyle to their list at the 7th place, modern researchers use the Roman numeral XIII to designate Ptolemais.