The radio frequency response of InAs nanowire array transistors on mechanically flexible substrates is characterized. For the first time, GHz device operation of nanowire arrays is demonstrated, despite the relatively long channel lengths of ∼1.5 μm used in this work. Specifically, the transistors exhibit an impressive maximum frequency of oscillation, f(max) ∼ 1.8 GHz, and a cutoff frequency, f(t) ∼ 1 GHz. The high-frequency response of the devices is due to the high saturation velocity of electrons in high-mobility InAs nanowires. The work presents a new platform for flexible, ultrahigh frequency devices with potential applications in high-performance digital and analog circuitry.