In classical Greek mythology, Syrinx /ˈsɪrɪŋks/ (Ancient Greek: Σῦριγξ, romanized: Súrinx, lit. 'pipe') was an Arcadian nymph and a follower of Artemis, known for her chastity. Being pursued by Pan, she fled into the river Ladon, and at her own request was metamorphosed into a reed from which Pan then made his panpipes.

Syrinx was a beautiful wood nymph who had many times attracted the attention of satyrs, and fled their advances in turn. She worshipped Artemis, the goddess of wilderness, and, like her, had vowed to remain a virgin for all of time. Pursued by the amorous god Pan, she ran to a river's edge and asked for assistance from the river nymphs. In answer, she was transformed into hollow water reeds that made a haunting sound when the god's frustrated breath blew across them. Pan cut the reeds to fashion the first set of panpipes, which were thenceforth known as syrinx. The word syringe is derived from this word.

Ovid includes the story of Pan and Syrinx in Book One of the Metamorphoses, where it is told by Mercury to Argus in the course of lulling him asleep in order to kill him. The myth is also preserved in the works of some anonymous Greek paradoxographer.

The story is also told in Achilles Tatius' novel Leucippe and Clitophon where the eponymous heroine is subjected to a virginity test by entering a cave where Pan has left syrinx pipes that will sound a melody if she passes. This has similarities with another myth Achilles wrote down, that of Rhodopis, who was transformed into a fountain that served as a virginity testing place for maidens.

Longus makes reference to Syrinx in his tale of "Daphnis and Chloe" in Book 2:34. Whilst the description of the tale here is modified to that of Ovid, it nevertheless incorporates Pan's desire to have her. Longus, however, makes no reference to Syrinx receiving aid from the Nymphs in his version, instead Syrinx hides from Pan in amongst some reeds and disappears into the marsh. Upon realising what had happened to Syrinx, Pan created the first set of panpipes from the reeds she was transformed into, forcing her to be with him for the rest of his days.

The story became popular among artists and writers in the 19th century. Elizabeth Barrett Browning wrote a poem entitled "A Musical Instrument" describing Pan's ruinous actions in creating the musical pipes. The Victorian artist and poet Thomas Woolner wrote Silenus, a long narrative poem about the myth, in which Syrinx becomes the lover of Silenus, but drowns when she attempts to escape rape by Pan. As a result of the crime, Pan is transmuted into a demon figure and Silenus becomes a drunkard. Amy Clampitt's poem Syrinx refers to the myth by relating the whispering of the reeds to the difficulties of language.

The story was used as a central theme by Aifric Mac Aodha in her poetry collection Gabháil Syrinx.

Samuel R. Delany features an instrument called a syrynx in his science-fiction novel Nova.