Originating with the Copenhagen School of security studies in international relations, the concept of the “securitisation of migration” refers to the social and political processes through which migration, as a public issue, acquires security character. This article reconstructs central tenets of the Copenhagen School’s speech act theory of security and discusses how it has been applied to the case of migration. While the Copenhagen School understood the securitisation of migration as the discursive construction of a threat to communal identities, subsequent accounts have emphasised the prevalence and, sometimes, discourse-independence of the material practices of securitisation. In doing so, they have substantially re-interpreted central tenets of the Copenhagen School’s securitisation theory, including the role and requirement of an audience for securitisation to take place and the forms of threat construction at work in the securitisation of migration. The article concludes by discussing the implications of the securitisation of migration for migration ethics. It argues that they depend on whether one understands the securitisation of migration as a theoretical framework or a social and political condition. Read as a theoretical framework, the securitisation of migration provides a way of classifying security arguments at work in migration ethics according to formal criteria. Read as a social and political condition, it makes a point about the presuppositions within which debates about migration ethics are situated in public.