Abstract <p>Marine ecosystems are a rich source of bioactive compounds, with carotenoids like astaxanthin, fucoxanthin, and zeaxanthin demonstrating significant antioxidant properties. These carotenoids neutralize reactive oxygen species (ROS), protecting against oxidative damage. This review examines their molecular structures, biosynthesis pathways, and mechanisms of action, including radical scavenging and involvement in key signaling pathways. Antioxidant assays confirm their potent ability to mitigate oxidative stress, with therapeutic implications for chronic diseases such as cancer, cardiovascular disorders, neurodegenerative diseases, and diabetes. Carotenoids also show promise in food, cosmetic, and nutraceutical applications, emphasizing the importance of sustainable sourcing. This review highlights the role of carotenoids in preventive health strategies and their potential to address oxidative stress-related diseases.</p> Graphical Abstract <p></p>