We investigated the hydrogen sensing capabilities of Pt Schottky diodes using nonpolar (10 (1) over bar0) m-plane GaN (m-GaN) bulk crystals. The Pt Schottky diodes on m-GaN wafer exhibited the fast and reversible response upon exposure to various hydrogen concentrations. The maximum sensitivity of m-GaN diode sensor was measured as high as 2x10(4)% at the forward bias of 0.1 V upon 4% hydrogen exposure. The Pt Schottky diodes on m-GaN sensors showed the selective sensing to hydrogen and negligible response to other gas species including CO, CH4, CO2, NO2, and NH3 at 25 degrees C. Our finding shows that Pt/m-GaN diode hold great potential for highly-sensitive hydrogen gas sensors due to the presence of nitrogen atoms having a much higher affinity to hydrogen than gallium atoms on nonpolar m-plane surface.