An aulos (Greek αὐλός, plural αὐλοί, auloi) or tibia (Latin) was an ancient Greek wind instrument, depicted often in art and also attested by archaeology.

An aulete (Greek: αὺλητής, aulētēs) was the musician who performed on an aulos. The ancient Roman equivalent was the tibicen (plural tibicines), from the Latin tibia, "pipe, aulos." The neologism aulode is sometimes used by analogy with rhapsode and citharode (citharede) to refer to an aulos player, who may also be called an aulist.

There were several kinds of auloi. A single pipe without a reed was called the monaulos (μόναυλος, from μόνος "single"). A single pipe held horizontally, as the modern flute, was the plagiaulos (πλαγίαυλος, from πλάγιος "sideways"). The most common variety must have been a reed instrument. Archeological finds, surviving iconography and other evidence indicate that it was usually double-reeded, like an oboe, although simple variants with a single clarinet-type reed cannot be ruled out.

Though aulos is often erroneously translated as "flute", it was a reed instrument, and its sound — described as "penetrating, insisting and exciting" — was more akin to that of the bagpipes, with a chanter and (modulated) drone. Like the Great Highland Bagpipe, the aulos have been used for martial music, but it is more frequently depicted in other social settings. It accompanied physical activities such as wrestling matches, the broad jump, the discus throw and to mark the rowing cadence on triremes, as well as sacrifices and dramas.Plato associates it with the ecstatic cults of Dionysus and the Korybantes, banning it from his Republic but reintroducing it in "Laws".