Engine control is the enabling technology for efficiency, performance, reliability, and cleanliness of modern vehicles equpped with a combusion engine for a wide variety of uses and users. It has also a paramount importance for many other engine applications like power plants. Engines are essentially chemical reactors, and the core task of engine control consists in preparing and starting the reaction (mixing the reactants and igniting the mixture) while the reaction itself is not controlled. The technical challenge derives from the combination of high complexity, wide range of conditions of use, performance requirements, significant time delays, and several constraints. In practice, engine control is to a large extent feed-forward control, feedback loops being used either for low-level control or for updating the feed forward. Industrial engine control is based on very complex structures calibrated experimentally, but there is a growing interest for model-based control with stronger feedback action, supported by the breakthrough of new computational and communication possibilities, as well as by the introduction of new sensors.