This Special Issue (SI) of Foods, entitled “Marine Algae Bioactives: Isolation, Characterization, and Potential Application”, was focused on algal organisms, both microalgae and macroalgae, which have recently been recognized as new, cost-effective, and valuable sources of health-promoting nutrients and bioactive compounds with a full spectrum of activities and beneficial effects on health. The focus of this SI was also on the methods and technologies used in the isolation, purification, and identification of these bioactives, as well as their application in various fields and industries. In this context, this SI consists of six original research papers and two review papers [7,8] that address recent advances and current knowledge in the proposed field. The isolation methods and the content of proteins, carbohydrates, minerals, lipids, and neutral fats from the four microalgae Chlorella vulgaris Beijer, Arthrospira platensis Gomont, Arthrospira platensis (Nordst.) Geitl., and Dunaliella salina Teod. were investigated in the study by Babich et al. [1]. In addition to the detection of high amounts of valuable nutrients in the algal samples examined, the authors reported that the composition of the nutrient medium influenced the lipid content and chemical profile of the algae.