CAD (computer-aided design) refers to the use of computer systems to design detailed two- or three-dimensional models of physical objects, such as mechanical parts, buildings, and molecules. CAD software is the software that allows a CAD designer to create these models.

CAD software is used in a wide variety of applications, ranging from the development of prototype products, to the development of entire automobiles. CAD is also used throughout research, allowing engineers to better understand problems they are attempting to solve, as well as consider solutions at a fraction of the cost of developing a physical model.