In recent years, there has been a wide research in supported single-atom catalysts (SACs), which contain only isolated individual metal atoms dispersed on an appropriate support or coordinated with the surface atoms of the support. The SACs exhibit many fascinating characteristics including high activity, selectivity, and maximum atomic utilization. These characteristics arise from the low coordination status, quantum size effect, and the strong metal-support interaction, which have proved to be very powerful in many typical heterogeneous catalysis field including oxidation, hydrogenation, the water-gas shift reaction, methanol steam reforming, electrocatalysis, and photocatalysis. In this review, we summarized the recent progress in synthesis, characterizations, properties, and applications of SACs.