Surface‐acoustic‐wave (SAW) characteristics of a lead potassium niobate (Pb2KNb5O15) single crystal have been calculated. It is predicted that SAW on this material has very strong electromechanical coupling 2&Dgr;v/vof more than 10% in the stiffened Rayleigh mode in theX‐axis boule andY‐cut plate and as high as 28.5% in the Bleustein‐Gulyaev mode in theZ‐axis cylinder.