We report novel metal–oxide–semiconductor field effect transistors (MOSFETs) based on individual gallium nitride (GaN) nanowires with fully conformal cylindrical gates. The W/Al O gates were deposited by atomic layer deposition. Reverse-bias breakdown voltages exceeded the largest gate voltage tested (−35 V). The nanowire MOSFETs showed complete pinchoff, with threshold voltages between −4 and −12 V. Maximum transconductances exceeded 10 μS, and ON/OFF current ratios higher than 10 were measured. Significant gating hysteresis and memory effects were also present, indicative of charge traps. Although further optimization is needed, these results represent a promising step forward in the development of efficient GaN nanowire-based FETs.