© 2021 World Scientific Publishing Company.This paper presents a systematic investigation of high-temperature transport characteristics of a single nanowire Gallium Nitride nanowire field-effect transistor (GaN-NWFET) ranging from room temperature to as high as 350ãC for the first time. The GaN-NWFET demonstrated a very good on/off current ratio (Iona•Ioff) of 3×103 for the p-side and 2.5×103 for the n-side at room temperature and considerably well at high temperatures. In fact, the device exhibited an on/off current ratio of 5.5×102 and a transconductance value of 0.96μS for the p-side at 350ãC indicating a good gating effect even at high temperatures. Additionally, the device exhibited very high mobilities with the hole mobility of 3.26×103cm2/V. s and electron mobility of 3.14×103 cm2/V. s at room temperature. Furthermore, the device showed very high transconductance values of 0.92μS and 20.3μS at the temperatures of 25ãC and 250ãC, respectively. As a consequence, the GaN-NWFET devices could find much use not only in high-power, but also in low-power transistor applications beyond the ambient temperature range (>300ãC) of silicon and silicon-on-insulator technologies for electronic and photonic circuits.