We have discovered that a class of inorganic sulfides [Li2S, (NH4)2S, Na2S⋅9H2O, etc.] imparts excellent electronic properties to GaAs surfaces. The surface recombination velocity at the interface between Na2S⋅9H2O and GaAs begins to approach that of the nearly ideal AlGaAs/GaAs interface. We propose the formation of a robust covalently bonded sulfide layer to explain the favorable electronic quality of such interfaces.