The CLIC (Compact Linear Collider) RF power source is based on a new scheme of electron pulse compression and bunch frequency multiplication. In such a scheme the drive beam time structure is obtained by the combination of electron bunch trains in isochronous rings. The next CLIC Test Facility (CTF3) at CERN will be built in order to demonstrate the technical feasibility of the scheme. It will also constitute a 30 GHz RF source with the CLIC nominal peak power and pulse length, which can be used to test accelerating structures and other RF components. CTF3 will be installed in the area of the present LEP pre-injector complex and its constructionand commissioning will proceed in stages over five years. In this paper we present an overview of the facility and provide a description of the different components.Presenting Author : Corsini R.