Stigma refers to a set of negative and unfair beliefs that a society or group of people have about something or someone. The term originated in ancient Greece, where it referred to symbols burned into the skin of enslaved people and people judged as criminals or traitors. Stigma may also be described as a label that associates a person to a set of unwanted characteristics that form a stereotype. Stigma can be affixed, and once people identify and label ones differences, others will assume that is just how things are, and the person will remain stigmatized until the stigmatizing attribute is undetectable.

Stigma can be associated with various characteristics, including age, body size, physical appearance, mental health, sexual orientation, and housing status. Stigma can be public, which describes the overarching sentiment society has about people with a certain trait, or perceived, which happens when an individual believes that others hold negative attitudes or beliefs about them.

Stigma can have harmful effects, including feelings of shame, hopelessness, and isolation, reluctance to ask for help or to get treatment, lack of understanding by family, friends, or others, fewer opportunities for employment or social interaction, bullying, physical violence, or harassment, and self-doubt.

Stigma is often associated with mental illness, and it can make it harder for people with mental health issues to recover. It may cause the person to avoid getting the help they need because of the fear of being stigmatized. Researchers identify different types of stigma, including public stigma, self-stigma, and institutional stigma. There are initiatives to reduce the stigma surrounding mental illness and substance use disorders, such as the Stamp Out Stigma campaign.