Photon upconversion through lanthanide-doped nanoparticles can be used to generate ultraviolet (UV) emissions for biomedical applications by excitation of near-infrared (NIR) light, which is readily accessible and highly penetrating in tissue environments. In article number 2201716, Feng Wang, Han-Lin Wei, and co-workers systematically review the latest progress in NIR-to-UV photon upconversion, including various strategies for controlling NIR-to-UV upconversion and the biomedical applications of these upconversion nanomaterials, which is expected to guide the future development of novel upconversion nanoparticles (UCNPs) for applications in biomedicine and beyond.