The ouroboros or uroboros is an ancient symbol depicting a serpent or dragon eating its own tail. The ouroboros entered Western tradition via ancient Egyptian iconography and the Greek magical tradition.

It was adopted as a symbol in Gnosticism and Hermeticism and most notably in alchemy. The term derives from Ancient Greek οὐροβόρος, from οὐρά oura 'tail' plus -βορός -boros '-eating'.

The ouroboros is often interpreted as a symbol for eternal cyclic renewal or a cycle of life, death, and rebirth. The skin-sloughing process of snakes symbolizes the transmigration of souls, the snake biting its own tail is a fertility symbol in some religions, and the tail of the snake is a phallic symbol, the mouth is a yonic or womb-like symbol.