In this letter, we present a fully monolithically integrated G-band push-push oscillator. The device is fabricated in a production-near SiGe:C bipolar technology. The transistors used in this work show a maximum transit frequency fT= 200GHz and a maximum frequency of oscillation fmax= 275GHz. The passive circuitry is realized by integrated transmission-line components, metal-insulator-metal (MIM)-capacitors and TaN resistors. The frequency of the output signal can be tuned between 183.3GHz and 190.5GHz, the maximum output power of the oscillator is -4.5dBm and the measured minimum single sideband phase noise is -73dBc/Hz at 1-MHz offset frequency. This represents the highest output frequency for oscillators using heterojunction bipolar transistor technology and published up to now.