Modern Flight Control Systems (FCS) consist of (1) aerodynamic control surfaces and/or the engines’ nozzles, (2) actuators, (3) sensors, (4) a sampler and ZOH device, and (5) compensators. The first four components of an FCS are hardware elements, whereas the controller (the digital implementation of the compensator) is an algorithm executed in real time in the on-board digital computer. In this chapter the design of the compensation/controller element/algorithm of the FCS, for a given aircraft, after the actuators, sensors and samplers have been chosen, is addressed. The way in which control theory is applied to the FCS’s controller design is the main focus of this article. An advanced and comprehensive perspective on flight control is presented. The emphasis is on maneuvering flight control. Thus, attention is given to the process of setting up the flight control problem from its inception. Flight Mechanics is used to obtain a rigorous formulation of the nonlinear dynamic model of the controlled “plant;” the linearization of the latter yields Linear Time Invariant (LTI) models routinely used for controller design. Also, it is important to remember that the pilot will be closing an additional outer feedback loop. This transforms the FCS design problem from one of meeting flying quality specifications into one of meeting handling quality specifications.