The concept of radiation pressure exerted against a reflecting surface by electromagnetic waves and by sound waves in gases is a familiar one. The absence of radiation pressure for sound waves in a “linear medium” is becoming well known. The equations are somewhat different for the radiation pressure for these two cases where the radiation pressure is not zero. The mechanisms usually called on to explain them (nonlinearity of the equation of state of the gas, acceleration of charges in the reflector by the electromagnetic waves) are widely removed from each other. Consequently, it is not evident on the surface whether radiation pressure is a general property of waves or the capricious result of isolated physical phenomena associated with some waves.A generalized concept of radiation pressure is here developed and then applied to several kinds of waves: sound waves in various media, waves on strings and springs, electromagnetic waves. Also, a simple demonstration of radiation pressure (for waves in a ripple tray) is described.