Speaking at a conference on Brexit in 2017, the former Danish Finance Minister Kristian Jensen stated "There are two kinds of European nations: there are small nations, and there are countries that do not yet realise they are small nations". This quote suggests how different countries have responded to European integration in different ways, and this paper seeks to examine the contrasting approaches to European integration in Ireland and in the UK, using this to explore the contemporary Brexit crisis. It focuses particularly on how each country has interpreted sovereignty in different ways – and with very different outcomes. Sovereignty was at the core of the Brexit referendum and the subsequent negotiations about the UK’s departure from the EU. This is hardly surprising, because the question of sovereignty is at the heart of the process of European integration in general.