With the rapid development of the Internet of Things, mmWave-based device-free wireless sensing is gaining momentum and beginning to influence our daily lives and work environments. mmWave-based device-free wireless localization technique, as one of the key techniques, enables the contactless detection and localization of humans by analyzing their impact on surrounding mmWave signals. In recent years, numerous mmWave localization techniques have been developed and are being planned for implementation in various human sensing applications, including the localization and tracking of persons in care homes and office buildings. In this chapter, a comprehensive summary is provided to encapsulate the technology and applications of mmWave-based device-free wireless localization. First, it presents mmWave hardware platforms and some key techniques of device-free wireless localization. Then, it provides a comprehensive review of existing mmWave-based device-free wireless localization works. Specifically, it divides existing works into three categories according to the localization capacity: single target localization, single micro-motion target localization, and multi-target localization. Finally, it discusses some potential applications of mmWave-based device-free wireless localization in the future. Advancements in mmWave-based device-free wireless localization techniques hold promise for various planned future intelligent applications, shaping the landscape of smart environments and enhancing our daily lives.