Our planet is changing at a pace never experienced before. Ecosystems worldwide are impacted by multiple anthropogenic pressures and are experiencing abrupt changes, sometimes leading to regime shifts. Marine ecosystems are prone to these dynamics and regime shifts are at the spotlight of research which seeks to reduce the uncertainties related to our incomplete understanding of these processes. Three main questions need to be answered to understand regime shifts: when they happen; i.e. detection, why; i.e. drivers and characteristics, and how; i.e. mechanisms. Present literature has focused mainly on detecting regime shifts, neglecting feedbacks and how ecosystems function. This ignorance has limited the causal understanding of these phenomena and has hindered the capacity to predict them, a fundamental step under global changes. FEEDRES brings feedbacks mechanisms at the fore and aims at responding to all the three challenges to understand and project regime shifts. To fulfil this, FEEDRES will develop a cutting-edge methodological framework combining methods from system dynamics theory and ecology. FEEDRES will follow three steps. 1) Map worldwide marine regime shifts – Through a systematic mapping FEEDRES will assess the extent of regime shifts, highlighting knowledge gaps (when). 2) Empirically study the important structural elements and connections that characterize marine systems under regime shifts (from populations to socio-ecological systems) – FEEDRES will apply a two-step modelling approach to understand how the system change during regime shifts (why). 3) Develop mechanistic models to understand how changes in feedback mechanisms mediate marine regime shifts (how). Based on the knowledge developed FEEDRES will identify common feedback types in marine systems and will project the likelihood of regime shifts. FEEDRES will revolutionise ecosystem science and will increase the understanding on how complex systems behave under cumulative stressors.