Recent progress in modeling thermophysical properties of electrolyte systems is reviewed. In particular, attention is focused on models for mixed-solvent electrolyte solutions and equations of state for high-temperature and supercritical electrolyte systems. The models are analyzed with respect to their capability of computing thermodynamic and transport properties in wide ranges of conditions and composition (e.g., for aqueous or mixed-solvent, dilute or concentrated solutions). A methodology is discussed to leverage the insights gained from electrolyte thermodynamics to predict corrosion of engineering metals. Further, applications of electrolyte models are reviewed for topics including the design of nuclear waste repositories, hydrometallurgy, crystallization and synthesis of inorganic materials in hydrothermal media.