In botany, a rhizome is a horizontal, usually underground stem of a plant that often sends out roots and shoots from its nodes. Also called a creeping rootstalk or rootstock. Many plants have rhizomes that serve to spread the plant by vegetative reproduction. Examples are asparagus and Lily of the valley. The spreading stems of ferns are called rhizomes.

A tuber is a thickened part of a rhizome, enlarged as a storage organ.

Carl Jung used the term "rhizome" to emphasize the invisible and underground nature of life:

Life has always seemed to me like a plant that lives on its rhizome. Its true life is invisible, hidden in the rhizome. The part that appears above the ground lasts only a single summer. Then it withers away—an ephemeral apparition. When we think of the unending growth and decay of life and civilizations, we cannot escape the impression of absolute nullity. Yet I have never lost the sense of something that lives and endures beneath the eternal flux. What we see is blossom, which passes. The rhizome remains. (Prologue from "Memories, Dreams, Reflections")

Gilles Deleuze and Félix Guattari coined "rhizome" to describe theory and research that allows for multiple, non-hierarchical entry and exit points in data representation and interpretation.