An object of the present invention is to provide a polymer electrolyte composition ensuring high durability even under high-temperature low-humidification conditions (for example, an operation temperature of 100.degree. C. with 50.degree. C. humidification (corresponding to a humidity of 12 RH %)), and a proton exchange membrane comprising the polymer electrolyte composition. The present invention provides a polymer electrolyte composition comprising (A) a polymer compound having an ion exchange group, (B) a polyphenylene sulfide resin, and at least one resin selected from (C) a polyphenylene ether resin and (D) a polysulfone resin, and a proton exchange membrane comprising the above polymer electrolyte composition.