Penis envy in Freudian psychoanalysis refers to the theorized reaction of a girl during her psychosexual development to the realization that she does not have a penis. Freud considered this realization a defining moment in the development of gender and sexual identity for women. According to Freud, the parallel reaction in boys to the realization that girls do not have a penis is Castration anxiety.
In contemporary culture, the term is sometimes used inexactly or metaphorically to refer to the idea that adult women wish they had a penis, or to refer to anxieties between men about the size of their genitals.