In this paper, we propose a power system stabiliser (PSS) design scheme based on robust decentralised output feedback sliding mode control technique. We demonstrate the proposed technique on a 10-machine, 39-bus power system and compare it with classical PSS design. Although the proposed technique is based on linearised model of the nonlinear multimachine power system, the efficacy of the controller has been demonstrated by the simulation using nonlinear model. © The Institution of Engineering and Technology 2007.