There is increasing interest in photochemical schemes for converting CO2 into a useful product as a means of mitigating atmospheric levels of this gas. Although photoelectrochemical schemes have been considered for this application, typically very high overpotentials are observed, and thus, semiconductor-electrolyte interfaces have not been observed to actually convert light energy to chemical energy in the aqueous CO2 redox system. We report here on a catalytic system that efficiently converts CO2 to methanol and other alcohols. The system couples a III-V p-type semiconductor electrode with a pyridinium catalyst. The conversion of CO2 to alcohols can be driven solely with light to yield faradaic efficiencies approaching 100% at potentials well below the thermodynamic potential. Mechanistic studies on the formation of methanol indicate that the observed six-electron reduction occurs via a series of one electron reductions mediated by pyridinium.