The application of composite materials for design of various structural systems is becoming more common every day. Composites are generally used because they can provide improvement of mechanical properties such as strength, stiffness, and toughness. Thus, stress analysis of composite materials would be required for design with such material. For that purpose, this chapter first provides the fundamental calculation theory necessary to evaluate composite lamina (a single layer of laminated composites). Once the lamina behavior is determined, then the stress analysis methods for composite laminate (bonded layers of lamina) structures is presented.