Composite membranes containing sub-micron diameter electrospun fibers of proton conducting sulfonated poly(ether ether ketone) have been fabricated. Interconnected fibers were formed into a dense mat and then embedded with an inert polymer matrix to create a water/gas impermeable proton conducting fuel cell membrane. The fibers were composed of 1.65 mmol/g ionexchange capacity polymer and the inert matrix polymer was a commercially available photocrosslinkable and solvent-less adhesive, NOA 63 (Norland Optical Adhesive). After electrospinning and before NOA embedding, the fiber mat was densified by heating and the fibers were welded to one another by exposure to ethanol solvent. The volume fraction of fibers in the resulting membranes was high (0.74) and the proton conductivity after embedding NOA 63 was 0.049 S/cm (for water equilibration at 25°C).