This paper addresses the problem of satisfying pointwise-in-time input and/or state hard constraints in nonlinear control systems, The approach is based on conceptual tools of predictive control and consists of adding to a primal compensated nonlinear system a Reference Governor (RG). This is a discrete-time device which on-line handles the reference to be tracked, taking into account the current value of the state in order to satisfy the prescribed constraints. The resulting hybrid system is proved to fulfill the constraints as well as stability and tracking requirements.