Happiness is an emotion associated with feelings ranging from contentment and satisfaction to bliss and intense joy. A variety of philosophical, religious, psychological and biological approaches have been taken to defining happiness and identifying its sources.

Philosophers and religious thinkers have often defined happiness in terms of living a good life, or flourishing, rather than simply as an emotion. Happiness in this older sense was used to translate the Greek Eudaimonia, and is still used in virtue ethics. In everyday speech today, however, terms such as well-being or quality of life are usually used to signify the classical meaning, and happiness is reserved for the felt experience or experiences that philosophers historically called pleasure.