Infrared (IR) technology plays a significant role in many application scenarios, such as satellite remote sensing, environmental monitoring, biomedical engineering, imaging, communications, and so on. Demands of the next generation IR photodetectors, including ease of fabricaation, low cost, high flexibility, and so on, greatly drive the development of colloidal IR quantum dots (QDs) as the most competitive candidate material for IR photodetectors. In this article, the progress of IR QD materials and photodetectors, the fundamentals of IR QDs, the integration of IR QDs with other materials for hybrid photodetectors, and the applications of the QD IR photodetectors are reviewed.