The electronic, magnetic and optical properties of Zn-doped monolayer SnS2 have been theoretically investigated with the density functional theory. Numerical results reveal that monolayer SnS2 can be easily synthesized by cleaving its bulk crystal. Besides, the Zn doping in monolayer SnS2 is energetically favored under the S-rich with respect to the Sn-rich condition. The doped system exhibits the magnetic ground states due to the formation of defect states above the Fermi level, which are introduced by the hybridization between S-3p states and a small amount of Sn-4d states. The room temperature ferromagnetism can also be realized in Zn-doped monolayer SnS2. The injection of Zn can enhance the absorption efficiency of solar spectrum, especially in the near-infrared light region. Moreover, the Zn doping can enhance the photocatalytic activity for both the oxygen and hydrogen evolution reactions in the monolayer SnS2 (C) 2016 Elsevier B.V. All rights reserved.