This paper presents an 8-to-10GHz CMOS voltage-controlled oscillator (VCO) with common-mode (CM) resonance. It features a nested 8-shape inductor-based CM resonator with intrinsic differential 2ND harmonic extraction. The mutual coupling of the main tank and CM resonator is negligible due to the reversal magnetic field, which avoids the additional chip area occupation of the explicit CM inductor. The VCO prototyped in 65-nm CMOS scores a −136.7-dBc/Hz PN with 10-MHz offset at 9.97 GHz, consuming 4 mW of power with a standard supply voltage of 1-V. The achieved peak Figure-of-Merit (FOM) is 190.6 dBc/Hz at 10-MHz offsets. Over a 22.9% tuning range, the VCO upholds a consistent FOM of >188.5 dBc at a 10-MHz offset. The core area is 0.116 mm2.