The COROT project has been developed in the framework of the CNES small satellite programme, with European and Brazilian cooperation. It will be launched in 2006. It is dedicated to seismology and detection of telluric planets. It will perform relative broad-band photometry in visible light during very long (150 d) observing runs in the same direction, plus a number of short (10-20 d) observing runs. Both programmes will work simultaneously on the same region of the sky. The seismology programme aims to map the HR diagram and study in detail approximately 50 targets brighter than magnitude 9. The exoplanet programme will search for telluric planets slightly larger than the Earth orbiting around stars of magnitude 12 to 16, located in the habitable zone and closer. The data collected will also allow valuable seismic studies. A number of additional scientific programmes will also be conducted. The mission characteristics derived from the scientific objectives, the instrument and its performances for seismology, as well as preliminary observing plans, are presented.