A V-band CMOS sub-harmonically injection-locked quadrature voltage-controlled oscillator (SILQVCO) is presented using 90-nm CMOS process in this paper. A transformer coupled topology is employed in the SILQVCO to enhance locking range and operation frequency. The measured free-running oscillation frequency is from 56.6 to 59 GHz with a tuning range of 2.4 GHz. With one-third sub-harmonic injection, the SILQVCO features an overall locking range of 3.5 GHz, a phase noise of -126.8 dBc/Hz at 1-MHz offset, and a RMS jitter of 54 fs. The measured quadrature phase error and amplitude error are 0.32° and 0.26 dB, respectively. As compared with the prior art, this work has the best finger of merits in the millimeter-wave band.