Oxidative stress, which arises from an imbalance between the body’s antioxidant defenses and the formation of reactive oxygen species (ROS), is increasingly recognized as a key role in the initiation and progression of aging and many chronic diseases. Despite the widespread use of synthetic antioxidants, worries about their negative effects and lack of effectiveness have heightened the hunt for safer, more potent substitutes. Because they can survive in harsh and changing conditions, algae have developed a wide range of bioactive substances with strong antioxidant qualities. These substances include phenolic compounds, carotenoids, vitamins, polysaccharides, and sterols. These substances not only protect the algae but also have great potential for human treatment. Notably, algae antioxidants such carotenoids, flavonoids, and phlorotannins have shown potent oxidative damage prevention and radical scavenging action. Their uses range from neuroprotection to cosmetics and the treatment of chronic diseases. There is a strong need to investigate and utilize the distinct antioxidant repertoire of algae due to the rising incidence of illnesses linked to oxidative stress and the shortcomings of existing antioxidant treatments. This chapter is driven by the pressing need for new, safe, and effective natural antioxidants as well as the encouraging data showing that chemicals produced from algae can reduce oxidative damage, control inflammation, and promote cellular health in a variety of biological settings. This chapter attempts to position algae as a valuable resource in the ongoing battle against oxidative stress and its harmful health effects by methodically examining the antioxidant mechanisms and health applications of algal metabolites. It informs future research and development in nutraceuticals, pharmaceuticals, and functional foods.