Cynicism was originally the philosophy of a group of ancient Greeks called the Cynics, led by Antisthenes.

Nowadays the word is generally used, somewhat pejoratively, to refer to somebody who is inclined to disbelieve in human sincerity or virtue: an individual who maintains that human behaviour is motivated entirely by self-interest. A modern cynic is typically highly contemptuous of social norms, especially those which serve more of a ritualistic purpose than a practical one, and will tend to dismiss a substantial proportion of popular beliefs and accepted wisdom as "bullshit".

Despite the negative portrayal of cynics, there are some who would argue that such people are simply those who "refuse to look through rosy-tinted spectacles" and are not afraid to demolish popular misconceptions no matter how sacred they are considered by society. Cynics themselves tend to take this view, regarding themselves as enlightened free thinkers, and their critics as deluded social pretenders who "bury their heads in the sand." However, an excess of cynicism in an individual can cause difficulties when they see themselves as depersonalised and self-serving inhabitants of a world which is meaningless, fictitious and shallow. Critics of cynicists often consider cynicism to be a form of nihilism and damaging to the function of life.