Well-being is what is ultimately good for a person. Also called "welfare" and "quality of life", it is a measure of how well life is going for someone. It is a central goal of many individual and societal endeavors.

Subjective well-being refers to how a person feels about and evaluates their life. Objective well-being encompasses factors that can be assessed from an external perspective, such as health, income, and security. Individual well-being concerns the quality of life of a particular person, whereas community well-being measures how well a group of people functions and thrives. Various types of well-being are categorized based on the domain of life to which they belong, such as physical, psychological, emotional, social, and economic well-being.

Theories of well-being aim to identify the essential features of well-being. Hedonism argues that the balance of pleasure over pain is the only factor. Desire theories assert that the satisfaction of desires is the sole source of well-being. According to objective list theories, a combination of diverse elements is responsible. Often-discussed contributing factors include feelings, emotions, life satisfaction, achievement, finding meaning, interpersonal relationships, and health.

Well-being is relevant to many fields of inquiry. Positive psychology studies the factors and conditions of optimal human functioning. Philosophy examines the nature and theoretical foundations of well-being and its role as a goal of human conduct. Other related disciplines include economics, sociology, anthropology, medicine, education, politics, and religion. Even though the philosophical study of well-being dates back millennia, research in the empirical sciences has only intensified since the second half of the 20th century.

Well-being is what is ultimately good for a person or in their self-interest. It is a measure of how well a person's life is going for them. In the broadest sense, the term covers the whole spectrum of quality of life as the balance of all positive and negative things in a person's life. More narrowly, well-being refers specifically to positive degrees, while ill-being denotes negative degrees. The precise definition of well-being is disputed and varies across disciplines and cultures. Some characterizations focus on a single element, like happiness, while others include multiple components, such as good physical and mental health, positive emotions, an engaged and flourishing lifestyle, inner harmony, and positive interpersonal relationships. Some definitions also include material conditions, such as income, safety, and low pollution. Although discussions of well-being usually focus on humans, the term also covers other animals in its widest sense.

As a person-specific value, well-being contrasts with impersonal value or value simpliciter. A thing has impersonal value if it is good for the world at large by making it a better place, without being restricted to one specific person. Well-being, by contrast, is what is good for or relative to someone. While personal and impersonal values often align, they can diverge, for example, if an individual seeks a personal gain that is bad from a wider perspective. The exact relation between these two types of value is disputed. According to one proposal, impersonal value is the sum of all personal values.

Well-being is typically understood as an intrinsic or final value, meaning that it is good in itself, independent of external factors. Things with instrumental value, by contrast, are only good as means leading to other good things, like the value of money. Well-being is further distinguished from moral, religious, and aesthetic values. For instance, donating money to a charity may be morally good, even if it does not increase the donor's well-being.

The terms quality of life, good life, welfare, prudential value, personal good, and individual utility are often used as synonyms of well-being. Similarly, the words pleasure, life satisfaction, and happiness are employed in overlapping ways with well-being, although their precise meanings differ in technical contexts like philosophy and psychology. Pleasure refers to individual feelings about what is attractive. Life satisfaction is a positive attitude a person has towards their life as a whole. Happiness is sometimes identified with life satisfaction or understood as a positive balance of pleasure over pain.