This paper proposes a novel wideband voltage-controlled oscillator (VCO) for multi-band transceivers. The proposed oscillator has a core VCO and a tuning-range extension circuit, which consists of an injection-locked frequency divider (ILFD) and flip flop dividers. The two-stage differential ILFD generates quadrature outputs and realizes two, three, four, and six of divide ratio with very wide output frequency range. The proposed circuit is implemented by using a 90nm CMOS process, and the chip area is 250 × 200µm². The measured result achieves continuous frequency tuning range of 9.3MHz-to-5.7GHz (199%) with −210dBc/Hz of figure-of-merit (FoM _T).