Immigration policies and immigrants’ rights to social protection in the UK have evolved dramatically over the past few decades, due to changing immigration flows, the UK’s membership of the European Union (EU) and participation in the European Single Market, and increasing anti-immigration sentiment, which culminated with the decision to leave the EU in January 2020. In this chapter, we argue that, at present, access to social protection is hierarchically structured depending on the interplay of three key variables: benefit type, immigration status and residency status. British citizens residing in the UK and immigrants with a permanent leave to remain have access to full social protection. So do generally European Economic Area (EEA) immigrants with the right to reside, though the precise basis of the right to reside is important in determining the types of benefits the person is entitled to. Migrants with a temporary leave to remain are excluded from most non-contributory benefits, as generally are British citizens living abroad, though those residing in EEA countries and those residing in a country with which the UK has a social security agreement are still entitled to a limited range of benefits. Many changes in access to social protection, especially as regards EEA immigrants in the UK and British nationals living in the EEA, are likely to stem from the UK leaving the EU, though these changes are currently being negotiated and, at present, no definitive post-Brexit regulatory framework is available.