The creation and application of proteins with desirable properties would benefit significantly from strategies to reduce the problem of protein aggregation. Here we demonstrate "supercharging" the surface of three disparate proteins to alter their net charge by as much as 55 charge units, without destroying protein folding or function. These supercharged variants acquire unusual resistance to aggregation and, unlike their natural counterparts, can refold and function even after boiling. Our findings demonstrate an approach to increasing protein robustness, suggest surprisingly broad, untapped plasticity at protein surfaces, and may help explain the modest net-charge distribution of natural proteins.