Mitochondrial reactive oxygen species (ROS) play a complex role in cellular signaling and disease pathogenesis, as they can act as signaling molecules to regulate various cellular processes, but also contribute to oxidative stress and damage. Antioxidants, such as glutathione and superoxide dismutase, help to regulate ROS levels by neutralizing or scavenging ROS, while other mechanisms, including mitochondrial dynamics and biogenesis, also contribute to ROS regulation. Dysregulation of ROS levels has been implicated in various diseases, including neurodegenerative disorders and cancer.