This chapter presents a summary of disability theory with reference to social work practice. We consider five models of disability, of which we advocate that three are essential for social work practice to support disabled service users. We discuss two medical models and three versions of the social model with reference to their theoretical origins. The chapter will suggest that the biomedical models employ an essentialist perspective to disability and impairment (see Chapter 6), whereas the social models draw on historical materialism, critical realism and post-structuralism philosophies. We use examples from our research to illustrate how these theoretical lenses emerge and can be applied in different situational professional spaces.