—In this paper, the first gallium nitride (GaN) based high electron mobility transistor (HEMT) power amplifier design using an artificial neural network (ANN) modeling technique is presented. The ANN technique was used to model the small signal behavior of a device with a gate periphery of 1 mm and a gate length of 1 m over the broad frequency range from 1 GHz to 26 GHz with multiple bias points, based on fitting calculated -parameters to measured -parameters. A single stage amplifier constructed using these parameters showed a gain of about 7 dB and an output power of 1.2 W at 8 GHz when biased at = 20V and = 220mA in class AB mode. The good agreement between measured and simulated results was shown in both -parameter modeling and in amplifier design. Index Terms—Device modeling, gallium nitride (GaN), HEMT, neural network technique, power amplifier.