As platform capitalism concentrates data and power in the hands of a few tech giants, data cooperatives offer an alternative rooted in the social economy: organisations owned and democratically governed by their members, who pool their data for mutual benefit while retaining control over it. This report traces the concept from its principles and regulatory context (the Data Governance Act, GDPR) to a practical business model canvas, and closes with real-world cases — from MIDATA and Salus.coop in health, to JoinData in agriculture, POSMO in mobility, and Pescadata among artisanal fishing communities in Latin America. It is a resource for anyone assessing whether a data cooperative could work in their own context.