A 31.2% locking range K-band divide-by-6 frequency divider with regenerative injection-locked topology is proposed using 90 nm CMOS process in this paper. The circuit is composed of a singly balanced mixer and a divide-by-5 injection-locked frequency divider (ILFD). The proposed frequency divider features high division, high speed, and wide locking range. The measured locking range is 7.1 GHz with an input power of -5 dBm. The measured output power and phase noise at 1 MHz offset are -5 dBm and -138.7 dBc/Hz, respectively This work has the widest locking range with good input sensitivity among the reported millimeter-wave ILFDs with division ratio higher than or equal to 5.