This chapter presents a framework for identifying the wave loads on cylindrical structures using the monitored data of wave elevation and structural motions. The proposed method can be applied to perform wave load monitoring and data collection for offshore structures in a stochastic wave field. The derivation of the wave load identification based on the potential flow theory is presented in detail. The linear identification method (as the basis of the proposed method) is first established to simplify the identification process. A nonlinear identification method considering the second-order wave effects is introduced to improve the identification accuracy for nonlinear wave loads. The concept of wave load identification on a complex structure is also addressed.