ECSS may refer to:
- European College of Sport Science, Cologne, Germany
- European Cooperation for Space Standardization, Noordwijk, The Netherlands
- Escuela Catolica De San Sebastian, Manila, Philippines
- Enterprise Communications Support Services, an initiative of the FAA. ECSS-SB is ECSS for Small Business.
- Estuarine, Coastal and Shelf Science, an academic journal on ocean sciences