Mostly unknown to the general public, a fragmented landscape of transnational organizations has been developing in Europe. These organizations work across borders, but not entirely in the EU, and they generally have some basis in European law or policies. An inventory by the authors suggests there are at least 370 transnational organizations in Europe. Transnational organizations challenge basic notions of accountability: it is often very difficult to understand what the organization is doing, to whom it is accountable or even where it is located. This is not to say that accountability is necessarily a problem but much more research and insight is definitely required. IMPACT This article aims to put the almost 400 transnational organizations as a fragmented set of partially European organizations on the agenda. By understanding them as partially European (and partially regional, local or national), the authors raise issues of accountability and transparancy of those organizations. The article will be of value to European and regional policy-makers relating to various transnational organizations but also to leaders and staff in those organizations who need to relate (and account) to their important external stakeholders. These organizations offer opportunities for continued European collaboration after Brexit
