The Stewart platform manipulator is a 6 degrees of freedom parallel robot with a superior performance over serial robots. A variable gain super twisting algorithm ensuring global finite time convergence to the desired sliding surface is proposed for the position stabilization of the Stewart platform. For a given position of the platform, the leg lengths are estimated using inverse kinematics and corresponding leg velocities are obtained using a super twisting observer. The desired position of the platform is achieved using the proposed controller even in the presence of matched disturbances. The effectiveness of the proposed controller has been proved with the simulation results. © 2014 IFAC.