The impact of European integration on regional structures of government has been studied increasingly over the last decades, and changes to the EU treaties paid more attention to the role of European regions. However, there are still significant gaps in access to reliable information and comparative data regarding the state of regional democracy in the EU multilevel system. The ERDM addresses these gaps by providing an innovative web-portal that includes interactive maps on regions in Europe, based on a novel data set. The aim is to provide access to these novel data on regional democracy in Europe in a user-friendly way to visualize the diversity of subnational governance and democracy in Europe’s regions. The ERDM is cooperation between the REGIOPARL project (located at the DED) with the research project “Strengthening Regional Democracy”, conducted by Arjan Schakel (University of Bergen) that contributes relevant data to the ERDM as part of the cooperation.