This document provides an introduction to postmodernism and related theories in international relations. It begins with definitions of postmodernism and modernism, noting that postmodernism has emerged in various disciplines. It then discusses key aspects of modernism versus postmodernism. The document proceeds to outline some major postmodern thinkers and their ideas, including Foucault, Derrida, Lyotard and Baudrillard. It also discusses post-structuralism and how it critiques and builds upon structuralism. Finally, it briefly defines post-colonialism and the work of Edward Said on orientalism.