Marine macroalgae (commonly known as seaweeds), a rich yet underexplored resource, have emerged as a promising source of bioactive compounds with potent antioxidant properties. While oxidative stress is a critical factor in the pathogenesis of numerous chronic diseases, including neurodegenerative disorders, cardiovascular conditions, and cancer, macroalgae-derived compounds such as polyphenols, carotenoids, peptides, and sulfated polysaccharides have demonstrated the ability to mitigate oxidative damage through multifaceted mechanisms. These compounds neutralize reactive oxygen species and modulate key cellular pathways involved in inflammation and apoptosis. Despite significant advancements, gaps persist in understanding the pharmacokinetics, bioavailability, and clinical applications of these bioactives. Additionally, the inefficiencies of traditional extraction methods call for adopting innovative, environmentally friendly techniques that preserve bioactivity. This review synthesizes current knowledge on the therapeutic potential of macroalgal bioactives, acknowledges the contributions of other marine algae where relevant, highlights challenges in their extraction, and proposes future directions for research and application.