The year 2021 offers a critical opportunity for concerted action to influence the future of freshwater biodiversity, ecosystem services and human well-being. The United Nations Decade on Biodiversity 2011–2020 has ended, and governments around the world are reviewing major international agreements relevant to biodiversity conservation, including the Convention on Biological Diversity (CBD)1, the Sustainable Development Goals (SDGs)2, and the UN Framework Convention on Climate Change (UNFCCC)3. A Post-2020 Global Biodiversity Framework4 is under development, with the grand mission to “Halt the loss of species, ecosystems and genetic diversity by 2030; restore and recover biodiversity to ensure a world of people “living in harmony with nature' by 2050”. Freshwater ecologists have acted quickly to draw attention to the global dimensions of the freshwater biodiversity crisis and address the lack of a comprehensive framework to guide policy responses (Bunn, 2016; Darwall et al., 2018). An Emergency Recovery Plan for freshwater biodiversity, published by 25 authors from 14 organizations (Tickner et al., 2020), sets out six major priorities for global action and policy development to “bend the curve of freshwater biodiversity loss.” It has been submitted to the working committees of the Post-2020 Global Biodiversity Framework, and further promoted as a dramatic OUPblog “Bring living waters back to our planet5” Comprehensive reviews have since enumerated many research questions, actions and policy refinements needed to “bend the curve” and protect the world's freshwater ecosystems (van Rees et al., 2020; Buxton et al., 2021; Harper et al., 2021; Maasri et al., 2021). Each review cuts across important scientific, societal, management and policy issues. The purpose of this brief challenge paper is, likewise, to strengthen and support the Emergency Recovery Plan, but in a different way, by advocating a broader package of strategic activities that too often operate in silos, with patchy coverage of the world's freshwater ecosystem types and biogeographic diversity. This package presents traditional areas of scientific and societal activity that require more strategic, integrated and collaborative global effort to deliver evidence-based freshwater conservation outcomes, conjoined with terrestrial and estuarine/marine conservation, depending on context: (i) inventory, evaluation and research; (ii) restoration and rehabilitation; (iii) protected area design and management; and (iv) socio-ecological science and governance. The paper is intended to motivate greater interest, commitment and collaboration of all stakeholders in the most urgent and ambitious conservation enterprise of the next decade—to protect and sustain freshwater biodiversity in the socio-ecological systems of the Anthropocene.