Photobiology is a challenging research area aiming to explore the interactions between light and living organisms and their biological consequences, with applications in the fields of photomedicine, photo(nano)technology, photosynthesis, and photosensory biology. Nowadays, there is a great interest in designing advanced materials with peculiar physicochemical properties and photoresponsive features that, interacting with light, produce a response that can be exploited for diagnosis and/or therapy. In this Special Issue, articles and reviews addressing the latest advances in the use of light-responsive materials for photobiology have been selected for publication, including phototherapeutic biomaterials proposed for light-induced therapies against cancer, microbial infections, atherosclerosis, aesthetic dentistry treatments (e.g., dental bleaching), and photobiomodulation (PBM) for treatment of neurological and neuropsychiatric disorders.