Algae or seaweed is a photosynthetic eukaryotic organism living in the marine environment that offers countless medicinal benefits to human health. The majority of researchers reported an extensive study on this anionic biopolymer for its chemical contents that have therapeutic properties, such as sulfated polysaccharides, methanolic extracts, fucoxanthin, fucoidan, alpha-amylase, and acidic polysaccharides. This book chapter discusses algal species, bioactive compounds that are beneficial in the treatment of chronic diseases and organ systems, and the bioprocess and efficiencies of seaweed polysaccharides. The findings and prospects for the use of algae or seaweed in medicine and human health were discussed. © 2022 Elsevier Inc. All rights reserved.