Sea state data are of major importance for climate studies, marine engineering, safety at sea and coastal management. However, long-term sea state datasets are sparse and not always consistent, and sea state data users still mostly rely on numerical wave models for research and engineering applications. Facing the urgent need for a sea state climate data record, the Global Climate Observing System has listed “Sea State” as an Essential Climate Variable (ECV), fostering the launch in 2018 of the Sea State Climate Change Initiative (CCI). The CCI is a programme of the European Space Agency, whose objective is to realise the full potential of global Earth observation archives established by ESA and its member states in order to contribute to the ECV database. We present here an overview of the project, the first release of the Sea State CCI dataset, and some ongoing research and future developments considered within the Sea State CCI project. The Sea State CCI dataset v1.1 is freely available on the ESA CCI Open Data Portal: https://climate.esa.int/en/odp/.