Mainstreaming Social-Ecological Sufficiency: Closing the sustainable consumption gap between societal demand and ecological limits Global patterns of production and consumption are fundamentally unsustainable, threatening key planetary boundaries—earth system processes vital for maintaining of ecological integrity and human well-being. Strategies for averting this ‘ecological overshoot’ have largely focused on ‘greening’ production by reducing the material intensity (efficiency), or the material throughput (consistency) of economic activity. However, neither of these approaches address what constitutes a sustainable scale of economic activity. Here, the novel notion of social-ecological sufficiency—a socially satisfactory standard of living within ecologically sustainable natural resource usage—represents a vital third (integrative) strategy for moving towards an economy within a 'safe operating space for humanity’. The overall aim of MaSES is to mainstream the notion of social-ecological sufficiency as a conceptual and empirical bridge between research on planetary boundaries and sustainable production and consumption, with far-reaching academic and societal implications for sustainable resource use. WP1 will synthesize disparate approaches to conceptualizing sufficiency and cement social-ecological sufficiency as a core idea in sustainability. WP2 will employ a global environmentally extended material and energy flow analysis to quantify key planetary boundaries (land-system change, biochemical flows, climate change and freshwater use) in terms of ‘ecologically sufficient’ levels of household consumption. WP3 will adapt methods from consensual deprivation assessments to identify ‘socially sufficient’ levels of household consumption across different social groups. WP4 will assess the feasibility of different strategies for closing the gap between ecologically ‘safe’ and socially ‘acceptable’ levels of household consumption. WP5 addresses project management.