With the rapid development of embedded technology, mobile computing, and the Internet of Things (IoT), an increasing number of sensing devices have been integrated into people’s daily lives, including smartphones, cameras, smart bracelets, smart routers, and headsets. The sensors embedded in these devices facilitate the collection of personal information such as location, activities, vital signs, and social interactions, thus fostering a new class of applications known as human-centric sensing. Compared with traditional sensing methods, including wearable-based, vision-based, and wireless signal-based sensing, millimeter wave (mmWave) signals offer numerous advantages, such as high accuracy, non-line-of-sight capability, passive sensing (without requiring users to carry sensors), high spatiotemporal resolution, easy deployment, and robust environmental adaptability. The advantages of mmWave-based sensing have made it a research focus in both academia and industry in recent years, enabling non-contact, fine-grained perception of human activities and physical signs. Based on an overview of recent studies, the background and research significance of mmWave-based human sensing are examined. The existing methods are categorized into four main areas: tracking and positioning, motion recognition, biometric measurement, and human imaging. Commonly used publicly available datasets are also introduced. Finally, potential research challenges and future directions are discussed, highlighting promising developments toward achieving accurate, ubiquitous, and stable human perception.