["JCMS: Journal of Common Market Studies, EarlyView. ", "\nAbstract\nThe Anti‐Coercion Instrument (ACI), the most powerful tool in the EU's geoeconomic arsenal, has its origins in the first Trump US presidency and has recently been brandished again as a potential response to Trump's coercive tariffs. Its centrality to the EU's ‘geoeconomic turn’ and the twists and turns of its legislative history have been extensively studied. However, the ACI is also significant because its making highlights the crucial role of European foreign policy think tanks and presents an opportunity to theorise the role of these consistently overlooked yet omnipresent actors in European Union foreign policy. Using elite interviews and qualitative content analysis, this article first reconstructs the prehistory of the ACI through the work of the European Council on Foreign Relations, whose task force brought together policy‐makers and corporates from six member states. Its work contributed substantive input, agenda‐setting and in‐advance consensus‐building. Second, by synthesising the existing literature, I theorise the three central analytically distinct but mutually reinforcing functions that think tanks perform in EU foreign policy (EUFP): providing politically original ideas, convening and policy entrepreneurship. Besides offering a new history of the ACI, the article, therefore, provides a meso‐level analytical framework for understanding what think tanks do in EUFP applicable across different theoretical approaches. In the case of the ACI, it also shows that accounting for the role of think tanks in EUFP has important implications for the scholarly debates about the ‘power of ideas’, decision‐making processes and business power in the EU's geoeconomic turn."]