Mimir is the giant in who guards the "Well of Wisdom", situated in Jotunheim under of the roots of the world tree Yggdrasil. He stands half-immersed in the water and on his powerful shoulders he is supporting the Kjolen Mountains. It is said that he has been standing there since the beginning of time and that with the passing of millennia he became part of the mountain itself.

The chief god Odin sacrificed an eye for a drink from the Well. In some sources, however, it is the head of the god Mimir who guards the Well of Wisdom, and not a giant.