Value theory is a concept concerned with the value or worth of people or things. Worth may be considered in terms of usefulness or economic value. Value theory can also involve legal, moral, aesthetic, or quantitative value. It can involve just one type of value, or a combination of different types.

It is generally accepted that values are at the root of all types of behaviors, including those that are morally, politically, or economically motivated. Values may be held individually, socially, or both. However, in some cases, individual values may seem worthless without social understanding and acceptance. Value theory deals with examining the individual and social repercussions of values.

In psychological terms, value theory concerns the examination of the development and assertion of human values. It also concerns the study of the ways in which human beings act on values or fail to act on them. Psychology-related value theory focuses on determining the reasons behind human preferences and choices in relation to values. Studying value theory also includes attempting to develop plausible explanations for the ways in which values may or may not govern behavior.

In sociological terms, value theory deals with the types of personal values that are commonly held within a community. It also examines ways in which certain conditions or situations may change those values. Additionally, sociological value theory is concerned with how different groups of people may believe in and prioritize values that influence how they behave in social situations.

When value theory is considered in terms of ecological economics, it is categorized into donor-type value and receiver-type value. Many ecological economists hold the belief that in order for wealth to exist, a value, as determined by a donor, must be present. This donor-determined value provides a measurement of things that are necessary to make something or to provide a service. By contrast, receiver-type value is often concerned with market value and related concepts.