In this communication, we introduce squaric acid derivatives as anhydrous proton conductors. We report the synthesis, characterization and proton conductivities of four squaric acid derivatives. The anhydrous proton conductivity of one of the derivatives was 2.3 × 10(-3) S cm(-1) at 110 °C, comparable to the conductivity of molten 1H-1,2,3-triazole or 1H-imidazole.