This chapter brings together two topics of utmost scientific, societal and political relevance: international migration and population ageing. Recent statistics underline the importance of these topics in Europe, but also in other parts of the world. The population of international migrants worldwide has increased by 41.6 per cent from 2005 to 2019 (UN, 2019). In the same period, the population of persons aged 65 and over also has increased, by 53 per cent (UN, 2019). At the intersection of these two groups is the population of migrants aged over 65, which has been increasing throughout Europe (Ciobanu, Fokkema, and Nedelcu, 2017; Warnes et al., 2004). The objective of this chapter is to discuss in depth the diversity of these three populations: older persons, migrants and older migrants, and thereby to acknowledge that societies are growing increasingly diverse and that ageing in this context poses new challenges (Ciobanu, 2019). These challenges need to be studied in order to expand the knowledge base in several fields of research, and inform policies (Ciobanu, Fokkema, and Nedelcu, 2017). The chapter starts by providing data on older migrants in European countries. The rest of the chapter is organized in three parts. The first part gives an overview of the literature and, based on this, discusses different categories of older migrants, and the internal heterogeneity within each of these groups. The second part focuses on the implications that this diversity in old age has at different levels, and for the social support system, and finally, the conclusion briefly proposes some future lines of research.