The Baltic Sea ecosystem is subject to a wide array of societal pressures and associated environmental risks (e.g. eutrophication, oil discharges, chemical pollution, overfishing and invasive alien species). Despite several years of substantial efforts by state and non-state actors, it is still highly unlikely that the regionally agreed environmental objectives of reaching “good environmental status” by 2021 in the HELCOM BSAP (Baltic Sea Action Plan) and by 2020 in the EU Marine Strategy Framework Directive (MSFD) will be met. This chapter identifies key research topics, as well as presents analytical perspectives for analysing the gap between knowledge and action in Baltic Sea environmental governance. It does so by outlining important trends and key challenges associated with Baltic Sea environmental governance, as well as by summarising the scope and results of individual chapters of this interdisciplinary volume. The analysis reveals the development of increasingly complex governance arrangements and the ongoing implementation of the holistic Ecosystem Approach to Management, as two general trends that together contribute to three key challenges associated with (1) regional and cross - sectoral coordination and collaboration, (2) coping with complexity and uncertainty in science-policy interactions and (3) developing communication and knowledge sharing among stakeholder groups. Furthermore, to facilitate analysis of environmental governance opportunities and obstacles both within and across specific environmental issues, this chapter reviews the scientific literature to pinpoint key research issues and questions linked to the identified governance challenges.