The European Central Bank has published an Occasional Paper that maps the EU’s capital markets supervisory architecture and key non-bank market players, concluding that supervision remains highly complex and largely national despite increasingly cross-border markets. The paper, which reflects the authors’ views rather than those of the ECB, sets out an analytical framework for considering more integrated EU-level supervision as part of the broader debate on capital market integration. The analysis identifies 52 national authorities and 16 organisational set-ups across the EU, with the European Securities and Markets Authority (ESMA) mostly limited to regulatory and supervisory convergence tools and direct supervision of a narrow set of entities. Using sector-specific mapping and a sensitivity analysis, the paper distils common principles for supervisory integration based on size and cross-border relevance, alongside close EU–national cooperation. It indicates that around 40% of central securities depositories and central counterparties could fall under EU-level supervision depending on calibration, identifies 15 potential central securities depositories and five to six central counterparties as candidates under illustrative criteria, and suggests ESMA’s enhanced convergence work in asset management could focus on the 10–15 largest groups. For crypto-asset service providers, it argues that direct EU supervision would be beneficial for the sector as a whole, with a subset of significant firms subject to more stringent requirements, and discusses governance and funding considerations by comparing models including the Single Supervisory Mechanism, the Anti-Money Laundering Authority and the European Commission’s proposed ESMA reforms.