Additive manufacturing technology allows producing objects layer-by-layer starting from three-dimensional (3D) digital models. These 3D models can be drawn using CAD software or can be obtained starting from a real-world object, through reverse engineering (RE) techniques. RE process is today widely used in numerous industrial applications. It is a powerful tool for additive manufacturing, and their combination can greatly enhance product design as well as shorten the product development cycle. This chapter describes the main reverse engineering techniques – contact and noncontact active and passive systems – and the main phases that allow obtaining a 3D CAD model starting from a physical object.