We use a combination of density functional theory (DFT) calculations and experimental approaches to explore the stability and electrocatalytic activity of a wide range of transitionmetal single atoms on a TiC support. Our theoretical prediction that single atoms can be stabilized on the modified TiC surface is confirmed by experimental findings using them on a TiC support. The predicted activities where Pt and Au single atoms would be the best for hydrogen evolution and selective oxygen reduction reactions, respectively, agree well with experimental results. This rational strategy using computational modeling of materials enables effective design of highly active and stable single-atom catalysts.