A high frequency power amplifier includes: a multi-finger transistor including transistor cells electrically connected in parallel; an input side matching circuit connected to gate electrodes of the transistor cells; and resonant circuits, each resonant circuit being connected between a gate electrode of a respective one of the transistor cells and the input side matching circuit. The resonant circuits resonate at a second harmonic of the operational frequency of the transistor or at a frequency within a predetermined range centered at the second harmonic and act as a short circuit or exhibit low impedance as seen from the gate electrode.