Abstract: To solve the problem of underactuated ship trajectory tracking with immeasurable states, an adaptive dynamic surfaceoutput feedback control approach is proposed in the presence of unknown environmental disturbances. The nonlinear observer is designed to estimate the velocity state variables by coordinate transformation of the system. The dynamic surface control technology is introduced to eliminate the “differential explosion” problem of traditional backstepping methods on the direct derivative of virtual control, which can reduce the computational burden. An adaptive control law incorporated with σmodification is used to estimate the bound of the unknown environmental disturbances, which can prevent parameters from drifting. Application of Lyapunov function analysis proves that the trajectory tracking error is uniformly ultimate bounded. Finally,numerical simulation results demonstrate the validity of the proposed strategy.