The name Πρόκνη derives from the ancient Greek noun περκνός (perknós), meaning "dark-spotted," a term also used to denote a type of eagle. It descends from the Proto-Indo-European roots *per- and *perḱ-, which denote variegation or spotted patterns.

Princess Procne was born to Pandion I, king of Athens, and the naiad nymph Zeuxippe. Her siblings included Philomela, Erechtheus, Butes, and possibly Teuthras. She married King Tereus of Thrace and bore him a son named Itys (also called Itylus).

Procne was given in marriage to Tereus, king of Thrace, sometimes as a reward for the military assistance he had given her father against the Laconians. Ominously, neither Hera nor Hymen (gods of marriage) nor the Graces attended their wedding; only the torch-bearing Furies appeared, portending misfortune. After bearing Tereus a son, Procne grew homesick and asked her husband to bring her younger sister Philomela to visit.

Tereus journeyed to Athens but became immediately infatuated with the beautiful young Philomela. Presenting himself as Procne's emissary, he convinced Pandion to let Philomela accompany him home. During the return journey, Tereus's passion overwhelmed him: he dragged Philomela into the woods and violated her, and to silence her threats to expose him he severed her tongue and imprisoned her under guard. He then returned to Procne claiming that Philomela had died during the journey, and Procne grieved her supposed loss.

Months later, during a Thracian festival honoring Dionysus, women gathered to exchange gifts with their queen. The voiceless Philomela wove a tapestry depicting her ordeal and sent it to Procne. Discovering the truth through this textile, Procne disguised herself in Bacchic attire, infiltrated the festival, located her sister's prison, and spirited her away to the palace undetected.

Though Philomela could not speak to fully explain her suffering, Procne vowed vengeance. When her young son Itys came in seeking his mother, Procne—viewing him as an extension of his father's wickedness—killed him with Philomela's assistance. They butchered his body, cooked it, and prepared a private dinner to which Procne invited Tereus alone, claiming an Athenian custom required wives to serve their husbands in isolation. The unsuspecting Tereus consumed his own son. When he asked where the boy was, Procne revealed grimly that "you have him there, inside," and Philomela then emerged and hurled Itys's bloody head at his face.

Horrified and grief-stricken, Tereus seized his sword and pursued both women to kill them; Greek sources typically locate their capture near Daulia in Phocis. As he cornered them, the gods intervened, transforming all three: Tereus became a hoopoe (a bird with a crown-like crest and a sword-like beak), while the women became birds. Greek tradition held that Procne became the melodious nightingale and Philomela the chittering swallow, though Roman authors often reversed these assignments. Procne's bird form was said to mourn her murdered child eternally through its song.

Some variant accounts exist. Hyginus recorded a version in which Tereus falsely reported Procne's death to her father and requested Philomela as a bride; after assaulting her, he gave her to King Lynceus as a slave, but Lynceus's wife—a friend of Procne's—sent Philomela on to her sister.

The Byzantine scholar Eustathius swapped the sisters' roles, making the unmarried Procne the rape and mutilation victim. One late author spared Itys from death, transforming him instead into a pheasant admired for its plumage. Pausanias insisted the entire story took place at Daulis and noted that Tereus later committed suicide in Megara, where locals made offerings at his tomb, while the women were transformed in Athens.

A nearly identical myth concerns Aëdon of Ephesus, whose story parallels Procne's. Aëdon and her sister Chelidon (with the husband Polytechnus) play equivalent roles in Anatolia rather than Thrace. After Polytechnus rapes Chelidon as a "prize" in a wager with Aëdon, the sisters plot a similar revenge, and all are transformed into birds—Aëdon and Chelidon into their namesake birds (nightingale and swallow), Polytechnus into a woodpecker or pelican, with other family members also metamorphosing.

Early references appear in Hesiod and Sappho, who call the swallow "daughter of Pandion." Homer mentions Aëdon, daughter of Pandareus, who killed her son Itylus, but his version differs significantly: her husband was Zethus of Thebes, not Tereus, and she killed the boy accidentally while targeting her sister-in-law Niobe's child out of envy. Evidence from seventh- and sixth-century BCE artwork suggests that the two narratives—the accidental killing by Aëdon alone, and the intentional murder by two conspiring sisters—eventually merged. The similarity between "Pandareus" (Aëdon's father) and "Pandion" (Procne's father) may have caused confusion, allowing the nightingale-and-swallow mythology to attach to the Athenian royal lineage.

Tereus first appears in Aeschylus's The Suppliants, described as husband to the "hawk-chased Nightingale" who killed her own son. Sophocles's now-lost play Tereus (fifth century BCE) provided the most influential full account. Only fragments and summaries survive, but scholars reconstruct it as beginning with Tereus arriving in Thrace and lying to Procne about Philomela's death while presenting a female slave (the mutilated Philomela in disguise). Procne apparently had a soliloquy lamenting her isolation as a Greek woman married to a barbarian; she discovers the truth via the tapestry, leading to the on-stage recognition of Philomela, her gruesome revenge, and Tereus's realization of his cannibalism. A divine messenger (likely Apollo) announces the threefold transformation by deus ex machina, and the play concludes with a moral judgment condemning both Tereus's folly and the women's excessive vengeance.

The rape and mutilation of Philomela have no clear precedent before Sophocles, and it was likely Sophocles who introduced the names "Procne" and "Philomela," replacing the earlier etymological connection to the birds' identities. The popularity of his play eclipsed the older Aëdon version in subsequent literature.

In myth Procne appears as a singing nightingale, yet in reality only male nightingales produce the characteristic song. Ancient Greeks and Romans connected "Philomela" (via folk etymology) to "lover of song," rationalizing the tongueless swallow's twittering. Later authors swapped which sister became which bird, making Philomela the melodious nightingale, but this severed the logical etymological connection and created confusion about who mourned the dead boy. Aeschylus described the nightingale as "hawk-chased," implying an earlier version in which Tereus became a hawk rather than a hoopoe—a more logical predator of nightingales.

All versions of Procne's (and Aëdon's) tale retain the sensational elements of a mother murdering her child and undergoing metamorphosis. The myth elaborates the tension between a woman's loyalty to her birth family and to her marital one. Like Euripides's Medea, Procne—a Greek woman married to a foreign king—becomes a stranger in a hostile land and kills her offspring to spite her husband. Sophocles's version especially emphasized Procne's misery, her lament about being "sold away like mere commodities," and her ultimate choice of loyalty to her father's honor over her husband. The myth foregrounds sisterhood as a bond exceeding even maternal ties: though Procne and Philomela are sexual rivals for Tereus, Procne ultimately champions her sister, choosing her over her own child.

The narrative also opposes household order against wildness. Tereus's violation literally occurs in the woods, marking him as savage and degenerate, and Procne joins the disorder when she enters Bacchic revelry to rescue Philomela. By bringing her sister into the palace she corrupts her household, and ultimately Procne and Tereus abandon civilization forever, becoming animals severed from human society. Unlike Sophocles's version, Ovid presents the metamorphosis not as divine punishment but as a consequence of the trio's own inhumanity.

The swallow genera Progne, Ptyonoprogne, and Psalidoprocne, and the treeswift family Hemiprocnidae, derive their scientific names from this myth.