The concept of tipping points is increasingly being addressed in both fundamental and applied environmental contexts, and is particularly salient in the context of anthropogenic threats, including climate change. Most research on tipping points has been conducted through the lens of a single realm (i.e., freshwater, marine, or terrestrial). Yet, there is both the need and opportunity to learn and share across ecosystems, and to engage in coordinated and comparative research. We aimed to identify priority questions that are germane to freshwater, marine and terrestrial realms, and that, if answered, would improve our ability to understand what tipping points are, why they occur, where they occur, and what to do about them. To help enable such efforts, we assembled a team with diverse expertise to identify key research questions, supplemented by an outreach call distributed via various electronic outlets (e.g., email, websites, social media). The responses were then thematized, evaluated, aggregated or disaggregated, and prioritized. Through workshops, and using a modified Delphi approach, we developed a final list of 18 priority research questions. Key themes that emerged included questions of societal relevance (i.e., why questions), drivers, ecological processes, and sensitivity (i.e., what questions), scale and connectivity (i.e., where questions), and tools, techniques, and resources for implementation (i.e., how questions). These questions frame a research agenda intended to help guide future fundamental and applied research related to tipping points in freshwater, marine, and terrestrial ecosystems.