Solar-driven evaporation has been proposed as an efficient way to harvest solar energy for water treatment and desalination. However, the complex preparation process and the degradation of photothermal absorbers restrict their practical applications in solar thermal technology. Herein, a solar-assisted fabrication of three-dimensional dimpled MoS2 membrane (DMM-SA) with an open macroporous (1-2 μm) network is fabricated by folding and overlapping nanosheets under solar illumination. DMM-SA exhibits superior water permeability (334-461 LMH/bar) and extraordinary chemical and structural stability. Compared to the 1T and mixed-phase DMM-SA samples, 2H-DMM-SA floating on the water surface generates high heat localization and achieves high evaporation efficiencies of 83.8 ± 0.8% and 91.5 ± 1.1% at 1 and 3 sun illumination, respectively. After multiple illumination and regeneration cycles, 2H-DMM-SA presents high water evaporation and salt rejection performance. After desalination, the salinity level of permeate water is far below the World Health Organization (WHO) standard. Numerical simulations verify that the inner spaces between two nanosheets and the nanochannels contribute to the high bulk water and vapor fluxes during desalination. The facile and efficient design of 3D 2H-DMM-SA provides a novel avenue for seawater utilization by harvesting solar energy.