Seaweeds—brown (Phaeophyceae), red (Rhodophyta), and green (Chlorophyta)—are earning major attention for their health and sustainability benefits. Nutrient-dense and naturally low in fat, they provide vitamins (A, B-complex, C, D, E, K), essential minerals (iodine, calcium, iron, magnesium, zinc), fiber, and polyunsaturated fatty acids. Just as important, seaweeds are rich in bioactive compounds—fucoidan, laminaran, alginate, phlorotannins, fucoxanthin (brown); carrageenan and agar (red); and ulvan plus antioxidant pigments (green)—that show antioxidant, anti-inflammatory,