Green hydrogen (H 2 ) as a sustainable energy carrier can be directly produced through water electrolysis , potentially replacing traditional fossil fuels to achieve carbon neutrality . Current water electrolysis technologies rely on ultrapure freshwater, which, however, is scarce (<1% of earth’s water) and unevenly distributed around the world. Due to the abundant reserves and reasonable economic feasibility , the conversion of seawater to H 2 powered by renewable electricity is considered as a promising candidate toward energy sustainability . Recently, the mechanism of seawater electrolysis has been progressively clarified, motivating the development of design principles, for example, the alkaline design criteria and the Cl – blocking layer, for improved catalyst performance. We discuss the vital aspects of seawater electrolysis, including the challenges and recent development in electrode materials . We outline potential strategies that enable highly active and selective catalysts for seawater electrolysis in the presence of contaminants such as metal ions , chloride, and bio-organisms, as well as describe issues in electrolyzer design. This perspective is concluded by presenting several development opportunities to advance this promising technique.