A new model for the viscosity of electrolyte solutions has been developed based on the combination of liquid-state theory and absolute-rate theory. Using the McMillan-Mayer framework, the ions are represented as charged hard spheres and the solvent as a continuum. The activation Helmholtz energy in absolute-rate theory is approximated by the equilibrium mixing Helmholtz energy calculated analytically from liquid-state theory with a mean spherical approximation. The new model can satisfactorily correlate all available experimental viscosity data up to 12 mol/L of 20 alkali-halide aqueous solutions at ambient conditions with an overall average relative deviation (ARD) of only 0.29%, while the Kaminsky equation yields an overall ARD of 0.81% with the same number of adjustable parameters. Both monotonic and anomalous concentration-dependent viscosity behavior are well described quantitatively. The adjustable parameters in the model have physical meaning and are related with the degree of ion hydration, in agreement with the Hofmeister series. The simplicity and accuracy of this new model make it particularly well suited for engineering applications.