MEFEPO (Making the European Fisheries Ecosystem Plan Operational) is a group of ecologists, economists, management experts and fisheries scientists who are trying to make ecosystem based fisheries management a reality in Europe. This Atlas is intended for policy makers, managers and interested stakeholders. Its purpose is to provide an ecosystem overview of the North Western Waters area (NWW) Regional Advisory Council (RAC) area. This new edition of the Atlas has been modified in response to stakeholder feedback to provide updated information on the physical and chemical features, habitat types, biological features, birds, mammals, fishing activity and other human activities of the NWW region. Background material on four NWW case study fisheries is presented (North East Atlantic Mackerel, Northern Hake, Dublin Bay Prawn and Scallops). This NWW Atlas was produced by the Marine Institute, Ireland as part of the EU funded MEFEPO project.