Efficient solar vapor generation under normal one-sun illumination is widely expected to relieve water scarcity all over the world. Herein, we prepare a highly efficient solar vapor generator via the deposition of Ag nanoparticles on diatomite. Ag/diatomite combined with a filter paper, an airlaid paper and a polystyrene foam showed excellent vapor generation performance (the evaporation rate and efficiency (η) were ∼1.39 kg m⁻² h⁻¹ and ∼92.2%, respectively) under one-sun illumination at room temperature (25.0 °C). To the best of our knowledge, these values outperform most of the previously reported vapor generation performances and vapor generation efficiencies (if not all). Compared to the performance of Ag/SiO₂ (η ≈ 66.2%) and commercial Ag nanoparticles (η ≈ 72.6%), the outstanding performance of Ag/diatomite was attributed to the synergy of the localized surface plasmon resonance (LSPR) effect of Ag nanoparticles and the confinement effect in micrometer size-diatomite. Considering the low cost ($10 per ton) and large-scale availability of diatomite as well as the easy construction of the vapor generation configuration that we proposed, this study provides prospects for practical applications towards relieving water scarcity.