Abstract: Excessive reactive oxygen species (ROS) is associated with an array of pathological conditions, including cancer, diabetes, cardiovascular diseases, and neurodegenerative diseases. However, ROS-responsive materials have drawn attention in the development of drug delivery systems. There are many types of ROS-responsive materials explored in drug delivery applications, including sulfur-based responsive polymers, selenium-based responsive polymers, tellurium-based responsive polymers, oxalate ester-containing polymers, phenylboronic ester-containing polymers and unsaturated lipids. When integrated with ROS-responsive drug delivery systems, a photosensitizer is used as a light-sensitive element to generate ROS, mainly singlet oxygen (¹O₂), which in turn activates the ROS-triggered drug delivery.