<p>The dynamic response of offshore wind turbines is strongly influenced by pile–soil interaction, which is inadequately represented by conventional fixed-base models, leading to inaccuracies in predicting foundation behavior and overall structural response. To address this limitation, this study develops an integrated analysis framework based on OpenFAST, which fully couples the monopile-supported turbine structure, control system, environmental wind–wave–current loads, and pile–soil interaction. The framework is formulated using Kane’s dynamic theory and incorporates a nonlinear p–y soil spring model to represent soil stiffness. Within this framework, the dynamic responses under both normal operating and extreme load conditions are systematically investigated. The results indicate that pile–soil interaction and turbine control actions both play critical roles in governing system dynamics. For the present benchmark configuration, correction factors are proposed to account for the discrepancies introduced by the fixed-base assumption. Furthermore, supplementary fatigue analysis combining OpenFAST and ABAQUS shows that pile–soil interaction significantly affects the magnitude of fatigue damage while having negligible influence on its spatial distribution along the pile. Non-integrated analysis tends to overestimate fatigue life at critical locations, particularly around 6&#xa0;m below the mudline. For the present benchmark turbine and investigated load cases, a case-dependent reduction factor of 0.85 is suggested for correcting fatigue life estimates obtained from non-integrated models. In addition, normal operating conditions, rather than shutdown states, are identified as the dominant contributor to monopile fatigue damage. The proposed integrated modeling framework provides a practical approach for improving the accuracy of dynamic response prediction and fatigue assessment in offshore wind turbine foundation design.</p>