In psychology, libido is psychic drive or energy, usually conceived as sexual in nature, but sometimes conceived as including other forms of desire. The term libido was originally used by the neurologist and pioneering psychoanalyst Sigmund Freud who began by employing it simply to denote sexual desire. Over time it came to signify the psychic energy of the sexual drive, and became a vital concept in psychoanalytic theory. Freud's later conception was broadened to include the fundamental energy of all expressions of love, pleasure, and self-preservation.

Sigmund Freud was an Austrian neurologist and the founder of psychoanalysis, a clinical method for evaluating and treating pathologies seen as originating from conflicts in the psyche, through dialogue between patient and psychoanalyst, and the distinctive theory of mind and human agency derived from it.