Heterosexism is upheld both by the legal privileging of heterosexual marriage, and by "phallocentric" thinking that assumes women's sexuality is defined primarily in relation to phallic intercourse.

Heterosexism generally refers to a system of social relations in which heterosexuality is institutionally and ideologically privileged at the expense of homosexuality. On the mundane level, heterosexism often manifests itself as the unconscious or explicit assumption that heterosexuality is the only 'normal' form of sexual relations.