This article explores the uses of the terms social exclusion and social inclusion in a mental health context. We briefly describe the origins of the term social exclusion and analyse its connotations in relation to four key dimensions: the relative, multifactorial, dynamic and transactional. We discuss Levitas's three discourses concerning social exclusion (the redistributionist, moral underclass and social integrationist) and present a case in favour of a fourth perspective, societal oppression. Focusing on social inclusion as a remedy for the ills of social exclusion, we discuss implications for contemporary mental health policy, practice and research. We highlight the potential contribution of social psychology to social inclusion theory. We conclude that a better theoretical understanding of causal mechanisms is needed to enable the development of more socially inclusive mental health services.