The CS-SDG project will lead to the organization of a citizen science conference which will bring together and showcase impactful citizen science initiatives, provide policy input to ongoing European developments and inspire the upcoming ten years of citizen science initiatives. CS-SDG will address this challenge by focusing on citizen science as a relevant approach to contributing to Global Challenges and industrial competitiveness in Horizon Europe, to the UN’s Sustainable Development Goals (SDGs) and to building upon ongoing initiatives in the Open Science strategy, the European Research Area (ERA) and Horizon 2020. The “A citizen science decade (2020-2030) in support to the Sustainable Development Goals” conference will represent a crucial opportunity to bring together lessons learnt from initiatives at global, national, regional and grassroots level, to scale up their impacts, address existing challenges and harness the potential of citizen science towards achieving the SDGs. One of the main conference outcomes will be a declaration and recommendations, gathering input in a collaborative way from conference participants and selected experts, focusing on the future of citizen science and its implementation in future funding programmes. CS-SDG will organise a conference gathering policy-makers and citizen science projects – from all parts of the world, from local to global scales, and both community-led and academic-led – to build the future of citizen science policy-making. The conference will be an opportunity to showcase the diversity of citizen science projects, and a forum for reflection and perspective, with transversal sessions to define together the latest developments, impacts, benefits and challenges of citizen science, as well as a global Citizen Science Festival. Most importantly, collaborative sessions will draw recommendations to feed in strategic policy recommendations for the decade 2020-2030.