Résumé : Aiming to speak to broader debates about the nature of state power in relation to the economy this thesis concentrates on central bank agency and monetary governability. More specifically, it focuses on a single case: The agency of the European Central Bank (ECB) and the making, unmaking, and re-making of monetary governability in the euro area from 1999 through 2014. This choice is motivated by the euro area representing a unique ‘natural experiment’ in establishing monetary governability from scratch under conditions of 21st century financialised capitalism. The thesis is divided into two parts. Chapters one and two develop an original analytical and conceptual framework for the study of central bank agency. Starting out from the premise that governability is not a natural feature of the economy but needs to be actively established, I argue that any attempt to answer the question of the ECB’s role in that process has to account for the fundamental hybridity of central bank agency both as a central bureaucratic authority and as a bank, as well as for its multidimensionality as it addresses different governability challenges posed by different audiences. It is on the basis of these inductively won observations that I embrace the theoretical vocabulary of performativity, conceptualising governability as a performative effect of the interactions between the ECB and its audiences. The arrangements that govern these interactions are described, using a Foucauldian concept, as ‘apparatuses’. On that basis, the second part of the thesis comprises three empirical chapters on the financial apparatus of monetary policy implementation, the communicative apparatus of expectation management, and the ideological apparatus of monetary trust. The sixth chapter brings the analysis of the three apparatuses up to date by focusing on three key episodes from the recent financial and economic crisis.