As the most promising energy storage system (ESS), rechargeable alkali-metal (AM) ion batteries have been attracting great attention. A suitable anode material is quite crucial for successful development of AM ion batteries. Using first-principles calculations, we propose that a two-dimensional (2D) group-IV monochalcogenide, germanium sulfide nanosheet (GSNS), can serve as high-performance anodes for the AM (AM = Li, Na, and K) ion batteries. The interaction between AM atoms and GSNS is strong enough to prevent the clustering of the intercalated AM atoms that may occur in other 2D materials. The low energy barriers for the diffusion of AM atoms on GSNS, 0.236 (Li), 0.090 (Na) and 0.050 eV (K), suggest the high charge/discharge rate of the GSNS anodes. Low average electrode potentials and a high AM storage capacity up to 512 mA h g−1 (for Na) can be achieved in the AM/GSNS systems. In view of the higher abundance of Na and K than that of Li, our work offers a promising anode material for the development of low-cost Na and K ion batteries with high performance.