We present a new correlation for the vapor pressure of mercury that is valid from the triple point to the critical point. The equation is a Wagner-type form, where the terms of the equation are selected using a simulated annealing optimization algorithm. To improve the reliability of the equation at low temperatures, heat-capacity data were used in addition to vapor-pressure data. We present comparisons with available experimental data and existing correlations. The estimated uncertainty at a coverage factor of 2 varies from 3% near the triple point to 1% for temperatures from 273 to 400 K; 0.15% for the intermediate temperature region from 400 K to the normal boiling point at 629.77 K; for temperatures above the normal boiling point but below similar to 900 K, it is 0.5%; and for temperatures between 900 K and the critical point, we estimate that the uncertainty is 5%.