An imbalance between ROS and antioxidant defenses gives rise to oxidative stress and it is a major factor in the development and progression of chronic diseases due to oxidative stress. We are going to explore the molecular and cellular pathways through which oxidative stress promotes the breakthrough and advancement of chronic illness, including cardiovascular disorders, diabetes, Alzheimer’s and Parkinson’s disease, chronic inflammatory conditions, and cancer. It triggers a series of cellular disturbances, resulting in DNA damage, mitochondrial dysfunction, lipid oxidation, and protein oxidation. These disruptions weaken cellular structure and activate inflammatory signaling pathways, which worsen tissue damage and drive disease progression. Additionally, chronic inflammation, metabolic disturbances, and the immune system create a harmful cycle that accelerates disease progression. This chapter also examines how factors such as age, lifestyle habits (like diet, smoking, and environmental exposures), and genetic factors influence oxidative stress levels, increasing the risk of chronic diseases in specific populations. It also analyzes the potential of both pharmacological and dietary antioxidant therapies to reduce oxidative stress and restore redox balance, focusing on innovative therapeutic methods, including targeted ROS-scavenging compounds and gene therapies aimed at enhancing antioxidant capacity. It also explains the significance of how the pathogenesis of chronic diseases is related to oxidative stress. It emphasizes the importance of developing novel therapies that reduce oxidative stress, slow the progression of illness, and improve patients’ lives.