Philetas of Cos was a Hellenistic poet and scholar active around 300 BCE. Born on the island of Cos, he served as tutor to Ptolemy II Philadelphus and taught the poet Hermesianax and the grammarian Zenodotus of Ephesus. He was renowned for both his poetry and his philological scholarship, with later writers humorously noting his meticulous, fragile nature as a scholar.

Major surviving works, known only from fragments, include the elegiac poem Demeter, the hexameter poem Hermes, and the epigrams Paegnia. His prose glossary Ataktoi Glossai, explaining rare words, is now lost.

Philetas is a foundational figure in Alexandrian literature, highly esteemed by later poets including Callimachus, Theocritus, Propertius, and Ovid. His refined, allusive poetry helped establish Hellenistic aesthetic ideals, and his dual role exemplifies the scholarly-poetic synthesis of the period.