Green hydrogen, produced through renewable energy sources via electrolysis of water, can substantially contribute to decarbonizing all three heavy industries: fertilizer plants, oil refineries, and steel plants. In fertilizer production, it can replace natural gas in the synthesis of ammonia, while in oil refineries, it facilitates cleaner hydrocarbon processing and reduces emissions. For steel production, green hydrogen can be utilized as a reducing agent in direct reduced iron processes, thereby eliminating the need for carbon-intensive coal. By integrating green hydrogen, these industries can transition towards more sustainable practices, aligning with global climate goals.