This chapter examines the European Union (EU)’s response to the European sovereign debt crisis of 2009–2012 and the institutionalisation of its financial assistance regime through the creation of the EFSM, EFSF and ESM. It argues that the Euro crisis represented a watershed moment, exposing the structural weaknesses of the Economic and Monetary Union (EMU) and compelling EU leaders to improvise instruments that ultimately redefined financial assistance governance. The analysis traces the origins and framing of the crisis, the design and operation of the EFSM and EFSF as temporary rescue mechanisms and the establishment of the ESM as a permanent institution. Central attention is paid to the intergovernmental nature of these instruments, the politics of conditionality and the tensions between solidarity and fiscal discipline. The chapter contends that the Euro crisis institutionalised a model of ‘unconstrained intergovernmentalism’ in EU financial assistance, privileging executive decision-making and summit diplomacy over supranational integration, with long-lasting implications for European economic governance.