The development of highly efficient and durable oxygen evolution reaction (OER) catalysts for seawater electrolysis is of great importance for applications. Here, an amorphous FeMoO₄ nanorod array on Ni foam is reported as a highly active OER electrocatalyst in alkaline seawater, requiring only overpotentials of 303 and 332 mV to achieve 100 and 300 mA·cm⁻², respectively. Moreover, it shows strong long-term electrochemical durability for at least 50 h.