Class E power amplifers are high efficiency amplifiers that use transistors as an on-off switch and an impedance matching network that shapes current and voltage waveforms to increase overall efficiency. Class E power amplifiers were developed in 1975. by Nathan O. Sokal. The main idea behind class E power amplifers is to correct the disandvanteges of the class D power amplifiers, where the output capacitance of the transistor at higher frequency increases dissipation and thereby reduces the overall efficiency of the amplifier. The main goal of this thesis was to design a 100 W, 30MHz class E power amplifier using a GaN HFET transistor. GaN HFET transistors, unlike silicon transistors, possess much better characteristics which can help us to increase overall efficiency of the amplifier. The essential parameters in which the GaN HFET transistors are much better than silicon transistors are: input capacitance, output capacitance, dynamic resistance, smaller dimensions and lower price. The transistor we used is GS66508T (GaN-Systems). When designing the class E power amplifier, we used simulation tools such as LTspice and ADS. We also have used Altium Designer to design a printed circuit board. After we measured the amplifier characteristics, we found that the data did not match the simulation results.