Philetaerus (/ˌfɪlɪˈtiːrəs/; Ancient Greek: Φιλέταιρος, Philétairos, c. 343 –263 BC) was the founder of the Attalid dynasty of Pergamon in Anatolia.

[2] Philetaerus was born in Tieium (Greek: Tieion),[3] a small town on the Black Sea coast in Anatolia.

He also contributed troops, money and food to the city of Cyzicus for defense against the invading Gauls.

Attalus I, the first Attalid king of Pergamon, explained that when Philetaerus was a baby, he was brought into a crowd where he was pressed upon and his testicles were crushed.

[12] With the exception of Eumenes II, all future Attalid rulers depicted the bust of Philetaerus on their coins, paying tribute to the founder of their dynasty.