This chapter explores the constant threat of social exclusion for citizens. Social exclusion is discussed against the background of modern stressors of the social order itself, which make social exclusion all the more challenging: value pluralism, interconnectedness and work-differentiation. It argues that, if the nation-state does not confront the threat of social exclusion and reintegrate citizens who are on the verge of exclusion or have become excluded, these stressors will exacerbate the problem of social exclusion. Given the need to overcome the challenge of social exclusion, the chapter delineates different types of social exclusion in line with ideal types of citizenships: instrumental, communitarian, civic-republican and cosmopolitan citizenships. In other words, the chapter reveals what social exclusion implies from the perspective of different ideal types of citizenship and, correspondingly, the ways in which different types of welfare states can carry the same ideal types and deal with the social exclusion of citizens given value pluralism, interconnectedness and work-differentiation.