The Five-hundred-meter Aperture Spherical Telescope, called FAST, is a National Mega-Science Project of China under construction, which covers frequency range of 70 MHz -3 GHz (up to 8 GHz for future upgrade), costing over 100 M US$. The FAST was born in the global SKA activities, and will be located in the unique Karst region, a sinkhole-like landform, in Guizhou province. FAST can be seen as a modified Arecibo-type radio telescope using many innovative techniques, with as much as twice the collecting area and a wider sky coverage. FAST has, first, an active reflector, conforming to a paraboloid of revolution from a sphere in real time through actuated control, which enables the realization of wide bandwidth and full polarization capability by using standard feed design. Secondly, it has a light focus cabin suspension system, integrating optical, mechanical, and electronic technologies, reducing effectively the cost of the support structure and control system. With such a huge collecting area of more than 30 football fields, FAST will become the largest single dish ever built. An overview of the FAST project will be presented, addressing the concept, science case, feasibility study, Miyun FAST demonstrator, and current status with recent progress from the construction. Its completion is expected in late 2016.