Abstract: Seawater electrolysis for hydrogen production offers a promising route to reduce freshwater consumption, promote the utilization of coastal renewable energy, and enable the simultaneous exploitation of marine mineral resources. Compared with conventional water electrolysis using purified water, natural seawater provides abundant water supply and contains valuable ions such as Mg2+ and Li+, which creates opportunities for developing integrated systems for hydrogen production, magnesium recovery, and lithium enrichment. However, the complex composition of seawater also introduces substantial scientific and engineering challenges. High concentrations of Cl- can induce chlorine evolution or hypochlorite formation at the anode, while Mg2+ and Ca2+ tend to precipitate under cathodic alkaline conditions, leading to electrode blockage, membrane fouling, mass-transfer attenuation, and long-term performance decay. In addition, organic matter, microorganisms, suspended solids, and fluctuating seawater composition further complicate the interfacial reaction environment and limit the practical operation of direct seawater electrolysis. This review focuses on the key interfacial processes involved in seawater electrolysis and resource recovery, including the competition between hydrogen/oxygen evolution reactions and chlorine evolution reactions, cathodic local alkalization, Mg(OH)2 precipitation, and Li? enrichment. Recent advances in alkaline seawater electrolysis, chlorine-mediated electrolysis, membrane-assisted seawater electrolysis, H2-Mg(OH)2 co-production, and electrochemical lithium extraction are systematically summarized. Particular attention is paid to catalyst and electrode design strategies, such as chlorine-resistant anodes, anti-scaling cathodes, high-selectivity oxygen evolution electrodes, solidophobic interfaces, redox-mediated electrodes, selective membranes, and flow-field regulation. These strategies are discussed in relation to their ability to suppress chlorine-related side reactions, regulate interfacial ion distribution, control Mg/Ca precipitation behavior, and maintain stable hydrogen production under realistic seawater conditions. Beyond single-function hydrogen generation, this review further discusses the design principles and interfacial reaction mechanisms of integrated hydrogen production-magnesium extraction-lithium enrichment systems. In such systems, cathodic hydroxide generation can be used to convert Mg2+ into recoverable Mg(OH)2, while the remaining mother liquor or concentrated brine can be introduced into Li? enrichment units based on selective membranes, ion-sieve adsorption, or electrochemical intercalation/deintercalation. Representative studies show that rational coupling of electrode reactions, membrane transport, precipitation separation, and flow electrolyzers can transform some traditionally unfavorable seawater components into recoverable resources. Finally, major challenges are analyzed, including active chlorine control, Mg/Ca precipitation regulation, membrane stability, ion selectivity, Li? enrichment energy consumption, product purity, techno-economic feasibility, and continuous-flow scale-up. Future development should move from material-level performance evaluation toward system-level validation under real seawater, industrially relevant current densities, long-term operation, and quantifiable energy and resource recovery metrics, thereby promoting seawater electrolysis as a sustainable platform for green hydrogen production and lithium/magnesium resource co-utilization.