Introjection is a psychological process where the subject replicates in itself behaviors, attributes or other fragments of the surrounding world, especially of other subjects. Cognate concepts are identification, incorporation and internalization.

According to the psychoanalyst Freud, the ego and the superego are constructed by introjecting external behavioral patterns into the subject's own persona.

Introjection is also the name of a defence mechanism, which handles threats from the outside that can potentially cause anxiety by infolding them into the internal world of the subject, where they can be neutralized or alleviated. More specifically introjection means incorporating attributes, attitudes or qualities of an absent person of high significance (for example, mother gone to work or relative gone to heaven) into oneself.

One example often used is when a child envelops representational images of his absent parents into himself, simultaneously fusing them with his own personality.