A vice is a habit, behavior, or practice that is considered morally wrong or depraved according to societal norms. Vices are often associated with a lack of self-control and restraint, which can lead to harm to oneself or others. Examples of vices include dishonesty, greed, envy, wrath, and addiction to drugs, alcohol, or gambling. Vices are usually associated with a fault in a persons character or temperament rather than their morality. Synonyms for vice include fault, sin, depravity, iniquity, wickedness, and corruption.

Vices are culturally constructed, and different cultures and societies have different ideas of what a vice is, at different times. For example, in Protestant Christianity, the desire for personal wealth is seen as a virtue, whereas medieval Catholicism saw it as a vice.

In law enforcement and judicial systems, vice is often used as an umbrella term for crimes involving activities that are considered inherently immoral, regardless of the legality or objective harm involved. Depending on the country or jurisdiction, vice crimes may or may not be treated as a separate category in the criminal codes.

In contrast to vices, virtues are moral habits that are viewed as good or desirable because they are constructive and prosocial. Examples of virtues include honesty, courage, kindness, and self-control.