Laziness (also known as indolence) is disinclination to activity or exertion despite having the ability to act or to exert oneself. It is often used as a pejorative; terms for a person seen to be lazy include "couch potato", "slacker", and "bludger". Related concepts include sloth, a Christian sin, and lethargy, a state of lacking energy.

Despite famed neurologist Sigmund Freud's discussion of the "pleasure principle", Leonard Carmichael noted in 1954 that "laziness is not a word that appears in the table of contents of most technical books on psychology". A 1931 survey found high-school students more likely to attribute their failing performance to laziness, while teachers ranked "lack of ability" as the major cause, with laziness coming in second. Laziness is not to be confused with avolition, a negative symptom of certain mental-health issues such as depression, ADHD, ASD, sleep disorders, substance use disorders and schizophrenia.