A high-order, multivariable, modern plasma controller has been designed using H optimal control techniques and tested on the Tokamak Configuration Variable (TCV) tokamak. An initial design for the control of the plasma current, position, and shape parameters is described. The design process was based on the CREATE-L linearized model of TCV, and the controller was implemented on a digital processor. The results demonstrated that the required performance was delivered and the controller response was in good agreement with predictions using the model.