The Ouroboros (Greek Οὐροβόρος or οὐρηβόρος, from οὐροβόρος ὄφις “tail-devouring snake”, also spelled Uroboros in English), is an ancient symbol depicting a serpent or dragon swallowing its own tail and forming a circle.
The Serpent biting its own tail is first seen as early as 1600 years BC in Egypt. From there it moved to the Phonecians and then to the Greeks, who called it the Ouroboros, which means devouring its tail.
Greek alchemists later adopted the ouroboros. The symbol was possibly a variant symbol for Hermes, Mercury, Thoth or other related deities, who under the name Hermes Trismegistus, was the mythical founder of alchemy.
Though the symbol of ouroboros is widespread, its meaning is not universal. Its ancient meanings (rooted in alchemy arts) included the values of wholeness, transformation, integration, balance, and self-sufficiency. Sometimes, it is meant to symbolize the joining of opposites, similar to the yin-yang; suggestive that opposites not only coexist but are also related in a cyclical manner. In this context, ouroboros is sometimes depicted as half light and half dark. It was also used as the symbol for alchemy in the Middle Ages, as the goal of the practice was to join the conscious with the unconscious mind.