Failure is the social concept of not meeting a desirable or intended objective, and is usually viewed as the opposite of success. The criteria for failure depends on context, and may be relative to a particular observer or belief system. One person might consider a failure what another person considers a success, particularly in cases of direct competition or a zero-sum game. Similarly, the degree of success or failure in a situation may be differently viewed by distinct observers or participants, such that a situation that one considers to be a failure, another might consider to be a success, a qualified success or a neutral situation.

It may also be difficult or impossible to ascertain whether a situation meets criteria for failure or success due to ambiguous or ill-defined definition of those criteria. Finding useful and effective criteria or heuristics to judge the success or failure of a situation may itself be a significant task.

Cultural historian Scott Sandage argues that the concept of failure underwent a metamorphosis in the United States over the course of the 19th century. Initially, Sandage notes, financial failure, or bankruptcy, was understood as an event in a person's life: an occurrence, not a character trait. The notion of a person being a failure, Sandage argues, is a relative historical novelty: "[n]ot until the eve of the Civil War did Americans commonly label an insolvent man 'a failure'". Accordingly, the notion of failure acquired both moralistic and individualistic connotations. By the late 19th century, to be a failure was to have a deficient character.

A commercial failure is a product or company that does not reach expectations of success.

Most of the items listed below had high expectations, significant financial investments, and/or widespread publicity, but fell far short of success. Due to the subjective nature of "success" and "meeting expectations", there can be disagreement about what constitutes a "major flop".

Sometimes, commercial failures can receive a cult following, with the initial lack of commercial success even lending a cachet of subcultural coolness.

Marketing researchers have distinguished between outcome and process failures. An outcome failure is a failure to obtain a good or service at all; a process failure is a failure to receive the good or service in an appropriate or preferable way. Thus, a person who is only interested in the final outcome of an activity would consider it to be an outcome failure if the core issue has not been resolved or a core need is not met. A process failure occurs, by contrast, when, although the activity is completed successfully, the customer still perceives the way in which the activity is conducted to be below an expected standard or benchmark.

Wan and Chan note that outcome and process failures are associated with different kinds of detrimental effects to the consumer. They observe that "[a]n outcome failure involves a loss of economic resources (i.e., money, time) and a process failure involves a loss of social resources (i.e., social esteem)".