The deep sea is the last frontier on Earth. Yet at a time of unprecedented global change this frontier is under increasing pressure from human activities. Between 2016 and 2020 the ATLAS project worked across the North Atlantic to improve our understanding of complex deep-sea ecosystems in a changing ocean. ATLAS assembled the interdisciplinary expertise spanning social and natural sciences, environmental economics, policy and governance needed not only to develop new knowledge but to bring this straight to those shaping ocean policies at national, regional and international levels. The work of ATLAS continues through the H2020 iAtlantic Project (2019-23).