Welcome to the catalogue of EOSC4Cancer Use Cases: European Open Science Cloud for Cancer Use Cases. EOSC4Cancer will make diverse types of cancer data accessible: genomics, imaging, medical, clinical, environmental and socio-economic. It will use and enhance federated and interoperable systems for securely identifying, sharing, processing and reusing FAIR data across borders and offer them via community-driven analysis environments. Cancer’s complex nature requires integration of advanced research data across national boundaries to enable progress. The Horizon Europe mission board for cancer has identified access to data, knowledge, and digital services – accessible across the European Research Area through federated infrastructures – as a key enabling condition for success. The better we organise cancer data across Europe, the better and faster we can bring the fruits of new biological and technical innovations to the benefit of EU citizens/patients. EOSC4Cancer’s well curated data sets will be essential input for reproducible and robust analytics and computational methods – including machine learning and artificial intelligence. EOSC4Cancer’s five use cases will cover the patient journey from cancer prevention over diagnosis to treatment, laying the foundation of data trajectories and workflows for future European Cancer Mission projects. EOSC4Cancer brings together a consortium of 29 organisations from 13 countries, including cancer research centres, research infrastructures, leading research groups, hospitals, and supercomputing centres. To make the developments sustainable, EOSC4Cancer will leverage the partners’ research infrastructures partners and the EOSC ecosystem. It will also serve the European Cancer Mission, by engaging with large international coalitions (e.g., ICGC-Argo, GA4GH, 1+MG/B1MG, Cancer Core Europe, European Cancer Information System, European Network of Cancer Registries, Innovative Partnership for Action Against Cancer Joint Action) and patients/survivors associations..