Hydrogen systems engineers develop electrolyser systems, hydrogen purification processes, high-pressure storage, fuel dispensing systems, and hydrogen-based industrial applications. They model reaction kinetics, thermodynamics, energy flows, and safety behaviours for hydrogen infrastructures. They evaluate materials compatibility, system efficiency, and lifecycle impacts. Their work contributes to green hydrogen, mobility, heavy industry decarbonisation, and renewable energy integration. As hydrogen economies expand worldwide, demand for hydrogen engineers is rapidly accelerating.