The Einstein Probe (EP) is a mission of the Chinese Academy of Sciences (CAS) dedicated to time-domain high-energy astrophysics. Its primary goals are to discover high-energy transients and monitor variable objects. To achieve this, EP employs a very large instantaneous field-of-view (3600 square degrees), along with moderate spatial resolution (FWHM ~5 arcmin) and energy resolution.  Its wide-field imaging capability is achieved by using established technology of novel lobster-eye optics, thereby offering unprecedentedly high sensitivity and large Grasp, which would supersede previous and existing X-ray all-sky monitors. To complement this powerful capability to discover and monitor sources over a wide area, EP also carries a conventional X-ray focusing telescope with a larger effective area to perform follow-up characterization and precise localization of newly-discovered transients. Public transient alerts will be issued rapidly to trigger multi-wavelength follow-up observations from the world-wide community. The satellite has a weight of ～1450 kg and average power of ～1212 W in total. In the normal survey mode, during one orbit of 97 minutes three fields will be observed on the night-side of the sky with a ~20 min pointing each. Over three orbits almost the entire night sky will be sampled, with cadences ranging from several to a few ten revisits per day depending on the sky location. The mission is aimed for launch by the end of 2023 with a nominal lifetime of 3 years (5 years as a goal).