Inspired by biological systems that have the inherent skill to generate considerable bioelectricity from the salt content in fluids with highly selective ion channels and pumps on cell membranes, herein, a fully abiotic single-pore nanofluidic energy-harvesting system that efficiently converts Gibbs free energy in the form of a salinity gradient into electricity is demonstrated. The maximum power output with the individual nanopore approaches ∼26 pW. By exploiting parallelization, the estimated power density can be enhanced by one to three orders over previous ion-exchange membranes. A theoretical description is proposed to explain the power generation with the salinity-gradient-driven nanofluidic system. Calculation results suggest that the electric-power generation and its efficiency can be further optimized by enhancing the surface-charge density (up to 100 mC m−2) and adopting the appropriate nanopore size (between 10 and 50 nm). This facile and cost-efficient energy-harvesting system has the potential to power biomedical tiny devices or construct future clean-energy recovery plants.