A nymph in Greek mythology and in Latin mythology is a minor female nature deity typically associated with a particular location or landform. Different from goddesses, nymphs are generally regarded as divine spirits who animate nature, and are usually depicted as beautiful, young nubile maidens who love to dance and sing; their amorous freedom sets them apart from the restricted and chaste wives and daughters of the Greek polis. They are believed to dwell in mountains and groves, by springs and rivers, and also in trees and in valleys and cool grottoes. Although they would never die of old age nor illness, and could give birth to fully immortal children if mated to a god, they themselves were not necessarily immortal, and could be beholden to death in various forms. Charybdis and Scylla were once nymphs.

Other nymphs, always in the shape of young maidens, were part of the retinue of a god, such as Dionysus, Hermes, or Pan, or a goddess, generally the huntress Artemis. Nymphs were the frequent target of satyrs.

Nymphs are personifications of the creative and fostering activities of nature, most often identified with the life-giving outflow of springs: as Walter Burkert. The Greek word νύμφη has "bride" and "veiled" among its meanings: hence a marriageable young woman. Other readers refer the word to a root expressing the idea of "swelling" (according to Hesychius, one of the meanings of νύμφη is "rose-bud").

The Greek nymphs were spirits invariably bound to places, and the difficulty of transferring their cult may be seen in the complicated myth that brought Arethusa to Sicily. In the works of the Greek-educated Latin poets, the nymphs gradually absorbed into their ranks the indigenous Italian divinities of springs and streams, while the Lymphae, Italian water-goddesses, owing to the accidental similarity of their names, could be identified with the Greek Nymphae. The mythologies of classicizing Roman poets were unlikely to have affected the rites and cult of individual nymphs venerated by country people in the springs and clefts of Latium. Among the Roman literate class, their sphere of influence was restricted, and they appear almost exclusively as divinities of the watery element. Nymphs are also portrayed as selfish and as attention seekers who walk around naked in the middle of forests.