A process of making a three-dimensional solid object of virtually any shape from a digital model. 3D printing is achieved using an additive process, where successive layers of material are laid down in different shapes. 3D printing is also considered distinct from traditional machining techniques, which mostly rely on the removal of material by methods such as cutting or drilling (subtractive processes).

A 3D printer is a limited type of industrial robot that is capable of carrying out an additive process under computer control (such as computer numerical control).

The first working 3D printer was created in 1984 by Chuck Hull of 3D Systems Corp. The 3D printing technology was applied first to prototyping (starting in the 1980s), creating rapid prototyping. Its expansion into production (job production, mass production, and distributed manufacturing) was foreseen at that time and took several decades to develop. Production roles achieved significant scale for the first time in the early 2010s. Since the start of the 21st century there has been a large growth in the sales of AM machines, and their price has dropped substantially. According to Wohlers Associates, a consultancy, the market for 3D printers and services was worth $2.2 billion worldwide in 2012, up 29% from 2011. Applications are many, including architecture, construction (AEC), industrial design, automotive, aerospace, military, engineering, dental and medical industries, biotech (human tissue replacement), fashion, footwear, jewelery, eyewear, education, geographic information systems, food, and many other fields.

In industry, machine tool builders have developed machines that include both subtractive and additive manufacturing in one work envelope, and retrofits of existing machines are underway. In distributed manufacturing, one study has found that open source 3D printing could become a mass market item because domestic 3D printers can offset their capital costs by enabling consumers to avoid costs associated with purchasing common household objects.