Guilt is a moral emotion that occurs when a person believes or realizes—accurately or not—that they have compromised their own standards of conduct or have violated universal moral standards and bear significant responsibility for that violation. Feeling guilty is unpleasant for people while they experience it, but it can prompt positive, pro-social efforts to restore relationships and make amends.

When understood as a collection of basic emotions, guilt is composed of self-directed anger, sadness for the victim, anxiety, and fear (e.g., of damaging or losing relationships with individuals and society). Guilt is closely related to the concepts of remorse, regret, and shame.

Guilt is an important factor in perpetuating obsessive–compulsive disorder symptoms.

Guilt and its associated causes, advantages, and disadvantages are common themes in psychology and psychiatry. Both in specialized and in ordinary language, guilt is an affective state in which one experiences conflict at having done something that one believes one should not have done (or conversely, having not done something one believes one should have done). It gives rise to a feeling which does not go away easily, driven by the conscience, or what Sigmund Freud called the superego. Freud rejected the role of God and blamed the existence of guilt instead on the individual's own "fear of loss of love" and relationships, beginning in childhood, with a fear that parents could reject the child. The child turns this fear inward, to create self-directed anger. For Freud's later explicator, Jacques Lacan, guilt was the inevitable companion of the signifying subject who acknowledged normality in the form of the Symbolic order.

Alice Miller claims that "many people suffer all their lives from this oppressive feeling of guilt, the sense of not having lived up to their parents' expectations....no argument can overcome these guilt feelings, for they have their beginnings in life's earliest period, and from that they derive their intensity." This may be linked to what Les Parrott has called "the disease of false guilt....At the root of false guilt is the idea that what you feel must be true."

Therapists recognized similar feelings of guilt in individuals that survived traumatic events that involved a loved one perishing, called survivor's guilt.

The philosopher Martin Buber underlined the difference between the Freudian notion of guilt, based on internal conflicts, and existential guilt, based on actual harm done to others.

Guilt is often associated with anxiety. In mania, according to Otto Fenichel, the patient succeeds in applying to guilt "the defense mechanism of denial by overcompensation...re-enacts being a person without guilt feelings."