The next general election in the Republic of Ireland is scheduled to take place on or before 20 February 2025. At present, it seems very likely that it will result in a seismic change in Irish politics. Sinn Féin emerged as the largest single party in terms of votes in the last election in 2020, and since then they have built a considerable lead in the opinion polls. Of course, in politics the only certainty is uncertainty, and three years is an awfully long time in politics! There is no guarantee that their surge will continue. But assuming it does, it raises interesting questions about Ireland's relationship with the EU. Sinn Féin is a strongly nationalist party which has consistently raised concerns about the impact of the EU on Irish sovereignty. It is also a member of the GUE/NGL group in the European Parliament which has criticised many of the core economic and social policies of the EU. This paper examines the extent to which Sinn Féin can be considered a left-wing party, and also looks at the evolution of Sinn Féin's stance on the EU. It argues that Sinn Féin gives evidence of a Europeanisation effect (qv. inter alia Ladrech 2010; Poguntke et al. 2007) - there is a very clear indication of a softening of the party's position on Europe as a result of Brexit - but also of a continuing Eurosceptic element (qv. inter alia Leconte 2010; FitzGibbon et al. 2017). Its emergence as a potential leader of government would undoubtedly create a more fractious Irish-EU relationship.