In the last decade, the development of high-efficiency electrolytes based on polymeric materials has drawn increasing attention. Polysaccharides are widespread biopolymers with properties suitable for the fabrication of high-efficiency polymer electrolytes. In specific, algal-based polysaccharides are promising eco-friendly and biodegradable alternatives to conventional polymer electrolytes. This review focuses on the recent progress of polymer electrolytes based on algal polysaccharides. We set the basic consideration for high-performance polymer electrolytes and discuss the materials science aspects of algal-based polysaccharides involved. Then, we review the recent progress of algal polysaccharides-based electrolytes, including the various physical and chemical treatments applied for the enhancement of ionic conductivity and mechanical properties. Lastly, we summarize the applications of the algal polymer electrolytes in batteries, fuel cells, supercapacitors, and dye-sensitized solar cells and their performance. Algal polysaccharides are presented as biodegradable, cost-efficient, high-performance, and eco-friendly alternatives for the development of high-performance solid polymer electrolytes for modern electrochemical applications.