The present invention is related to a gel electrolyte composed of a mixture comprising an acid and a high molecular compound. The acid is capable of causing the polymer compound to swell. The polymer compound may comprise a high molecular compound, such as, a partially methylated polybenzimidazole where at least one substituent R group of the polybenzimidazole structure is a methyl group. Additionally, the present invention is related to a fuel cell employing gel electrolyte of the present invention. The gel electrolyte of the present invention has good proton conductivity for a long period of time under conditions having a relative humidity in the range of about 0% to about 50% at an operating temperature in the range of about 100.degree. C. to about 300.degree. C.