This review highlights the substantial nutritional worth of seaweeds by examining their nutritional content and bioactivity. Seaweeds provide several health advantages, including cardio-protection, anti-tumor, anti-oxidative, antibacterial, anti-inflammatory, and immunostimulatory properties owing to their high content of polysaccharides, proteins, PUFAs, minerals, and bioactive chemicals. Bodybuilders love them because they are high in fiber and low in calories. Seaweeds are an interesting target for drug development because of their potential use in medicine and disease prevention. Nonetheless, a number of seaweeds remain underutilized, and further research on seaweed extracts is essential. For effective usage, further knowledge of bioactivity and mechanisms of action is also required. Seaweeds may also be used as fertilizer and biofuel.