This thesis investigates the design and simulation of a robust trajectory tracking con-trol for autonomous underwater vehicle (AUV) using supertwist sliding mode control. Autonomous underwater vehicles are submarines which are extensively employed for underwater exploration and scientific missions. The control issue of AUV is very chal-lenging due to the non-linearity, time variance, unpredictable external disturbances such as environmental force generated by sea current fluctuation, and the difficulty in accur-ately modelling the hydrodynamics effects of AUV dynamics. Among various nonlin-ear controllers, sliding mode control has been extensively investigated for the trajectory tracking control of autonomous underwater vehicles and it provided good control per-formance. However this controller has chattering effect. The chattering problem have been relieved by using a higher order sliding mode controller. In this thesis, the kin-ematics and dynamics model of AUV has been developed, and the model based control has also been designed by integrating kinematics and dynamics model of AUV to enable the vehicle to track the required pre-specified paths. The designed controller determ-ines the desired control inputs or thrusts for given desired trajectory so the vehicles can track the trajectory. The designed controller performance has been tested by developing MATALB/simulink model of a system and controller to track the desired trajectory with minimum chattering of control efforts. The robustness of the proposed controller has been tested by applying time varying external disturbances and parameter uncertainty. The performance of a controller is examined by integral absolute error(IAE) and root mean square error(RMSE). The simulation result confirmed the controller is robust to the bounded disturbance and the tracking converges to zero with finite time.The de-sired position is reached approximately at 5.05 sec and 6.95 sec for STSMC and SMC controllers respectively. Key Words: AUV, Chattering Reduction, STSMC, Trajectory Tracking