This chapter discusses Judith Butler’s Gender Trouble (GT) and its legacy in political theory. It sets out five themes of GT: the claim that identity is always the result of power; the interplay between sex, gender, and desire; the critique of “identity politics,” including any feminism that posits a stable category of “women”; the concept of performativity; and the possibility of change via subversive performance. The chapter then goes on to discuss the major impact that GT has had on feminist theory, queer theory, trans theory, and intersectionality, along with the surprising lack of impact on theories of multiculturalism and identity theory more broadly. Finally the chapter discusses some main criticisms of the book.