This paper proposes an extended state observer based sliding mode controller for the speed control of permanent magnet DC motor. The state space model of the system is simplified using a linear state transformation and input transformation to design a linear extended state observer which estimates the system states and the disturbances. Then, a sliding surface is designed which includes the estimated disturbance in addition to the system states to make the sliding mode controller insensitive to the load variations. The proposed controller is validated through numerical simulations and the results shows that the extended state observer based sliding mode controller is capable of maintaining desired speed in the presence of changes in load torque. The comparison of the proposed controller with the integral Sliding mode controller shows a better transient response. © 2015 IEEE.