Electrochemical water splitting is regarded as an effective technology for producing green hydrogen, which is crucial for addressing energy and environmental challenges. In particular, direct seawater splitting offers significant economic and environmental advantages. However, its efficiency is hindered by the high overpotential required for the oxygen evolution reaction (OER) and the competition from chloride oxidation. This review highlights the potential of interface engineering to overcome these limitations and develop efficient OER electrocatalysts. We comprehensively explore recent advancements in interface engineering for OER in both alkaline and seawater environments. We begin by introducing the mechanisms of freshwater and seawater electrolysis, emphasizing key considerations for OER catalyst design. Subsequently, we review the recent progress made in various interface engineering strategies, analyzing their impact on OER performance in both electrolytes. Finally, we outline promising future directions for developing efficient seawater oxidation catalysts through interface engineering.