The second biennial edition of the world's only dedicated international conference on citizen science and water, and the first edition held in Africa. The CS4Water Conference 2027 brings researchers, practitioners, policymakers, educators, and communities together in Cape Town to advance citizen science as a trusted, resourced, and permanent part of how the world monitors, manages, and involves people in water. Focus for 2027: advancing participation in citizen science for water — elevating knowledge from the Global South, integrating citizen science into education, embracing digital innovation/AI to enhance citizen science data systems, and increasing trust in citizen science within governance systems for policy adoption. Aims include advancing collaborative research and knowledge exchange (North-South bridge), strengthening community and institutional agency in the water commons, accelerating practical solutions to the freshwater crisis (SDGs, Africa Water Vision and Policy 2063, UNESCO IHP-IX Output 1.10), building lasting Global South capacity and networks, and championing ethical and inclusive science (FAIR data).