<p>This study presents a novel in situ experimental identification technique for wave loads on fixed structures. It utilizes measured in situ wave surface elevation data around the structure as input. By employing Green’s function and the boundary element method, a direct physical mapping between the free-surface data and the structural surface pressure is established. Furthermore, formulations for both first-order and second-order wave load identification are developed. Experiments on three different structural shapes were conducted, confirming the method’s reliability for the precise characterization of wave load amplitude and phase. Additionally, the method enables accurate prediction of the average largest wave-induced force based on the average of the largest waves around the structure. With minimal data requirements and strong adaptability to complex geometries, this approach offers a valuable tool for large-scale in situ experiments and field monitoring of marine structures.</p>