A proton conductor is an electrolyte where movable hydrogen ions are the primary charge carriers. Proton conductors are usually composed of polymer or ceramic where the pore size is very small; so small that larger negative ions are locked into the solid matrix, and only very small ions (postive hydrogen ions, i.e. bare protons) can participate in a direct current.

Proton conductors are usually solid materials. When in the form of thin membranes, proton conductors are an essential part of small, inexpensive fuel cells.

Water ice is one example of a common proton conductor.