偏见（英语：prejudice，源自“prejudge”即“预先判断”）指的是不给别人以公正的考查便贸然作出判断。这种判断没有任何证据，只凭先入为主的成见而然。原因是怀持偏见的人所见的不是个人而是群体。这些人看来，一个民族或者一个地区内的成员都“一律相同”，具有共同的特征、性格和习惯。怀持偏见的人往往拼命维护自己的偏见；即使事实证明他错了，他仍会坚持下去。《今日心理学》杂志指出，怀持偏见的人“喜欢留意和记忆‘某’人的行动与他所定的形像相符之处，但却拒绝与该形像相反的证据。”

偏见可以助长偏见，从而产生更加不良的后果。被偏见影响较深的人往往失去自尊心，以致他们实际在生活上变成像别人所期望的一样。压迫之下的受害者可能变成充满愤恨，对偏见更加敏感，以致有时在其实没有偏见存在的地方也看出偏见。任何外族人士若非被人以不当的怀疑相看便是被视为潜在的仇敌。

Prejudice is prejudgment, or forming an opinion before becoming aware of the relevant facts of a case. The word is often used to refer to preconceived, usually unfavorable, judgments toward people or a person because of gender, political opinion, social class, age, disability, religion, sexuality, race/ethnicity, language, nationality, or other personal characteristics. In this case, it refers to a positive or negative evaluation of another person based on their perceived group membership. Prejudice can also refer to unfounded beliefs and may include "any unreasonable attitude that is unusually resistant to rational influence". Gordon Allport defined prejudice as a "feeling, favorable or unfavorable, toward a person or thing, prior to, or not based on, actual experience". For the Evolutionary Psychology perspective, see Prejudice from an evolutionary perspective.