In this letter, a low phase-noise (PhN) oscillator is designed, implemented, and experimentally tested using an active and compact Giuseppe Peano fractal resonator as a filter with high-quality factor (QF) which acts as the frequency stabilization and selection element. The oscillation frequency corresponds to the frequency response peak of the complex QF filter. Due to the characteristics of this active filter, the oscillator PhN is highly reduced. The oscillator, operating at 3.36 GHz with 15-dBm output power, demonstrates a measured PhN of −131.5 dBc/Hz at 100-kHz offset frequency and 151.4 dBc/Hz at 1-MHz offset frequency. It is shown that the proposed oscillator outperforms the state-of-the-art microwave planar oscillators in reducing the PhN.