<p>A model-independent regulation control law based on a finite time disturbance observer is proposed for underactuated offshore crane systems with unknown external disturbances. Different from existing control strategies, the issues consisting of unknown disturbances and model-independent are taken into consideration when making the controller design. More specifically, for the sake of the controller design, the dynamics of the offshore crane systems are given and rewritten based on some newly constructed state variables. Next, new error variables are defined and corresponding dynamics are derived. Then, to estimate unknown disturbances in finite time, a disturbance observer is presented. After that, a model-independent regulation control method is proposed, which does not involve system parameters. Subsequently, based on Lyapunov techniques and LaSalle’s invariance principle, rigorous stability analysis of the closed-loop system is presented to support the theoretical derivations. Finally, simulation tests are provided to demonstrate the superior performance and strong robustness against external disturbances of the proposed controller.</p>