A proton conductive copolymer includes styrene repeating units that have proton conductive functional groups and dimethylsiloxane repeating units. A polymer electrolyte membrane includes the proton conductive copolymer and a fuel cell uses the polymer electrolyte membrane. The proton conductive copolymer has excellent chemical and mechanical properties, excellent ability to form membrane with dimethylsiloxane repeating units, and superior ion conductivity with styrene repeating units that have proton conductive functional groups. Polymer electrolyte membranes that have properties appropriate for the fuel cell electrolyte membrane can be obtained using the proton conductive copolymer. Fuel cells that have improved efficiencies can be obtained using the polymer electrolyte membrane.