In this paper, an ultra-low-voltage crystal quartz oscillator is proposed. The design of the proposed oscillator is essentially based on using a HEMT operating in an unsaturated dc regime and a quartz resonator as a resonant impedance transformer. The 25 MHz prototype shows steady oscillations at the supply voltage of less than 17 mV and the power consumption as low as 300 nW, i.e., 1-2 orders of magnitude lower than the other to-date oscillators. This approach is good for building ultra-low consumption radio devices including those working at low temperatures.