Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature below the melting point. The atoms in the powder particles diffuse across the boundaries of the particles, fusing the particles together and creating one solid piece. Because the sintering temperature does not have to reach the melting point of the material, sintering is often chosen as the shaping process for materials with extremely high melting points such as tungsten and molybdenum.

Sintering is traditionally used for manufacturing ceramic objects, but finds applications in almost all fields of industry. The study of sintering and of powder-related processes is known as powder metallurgy. A simple, intuitive example of sintering can be observed when ice cubes in a glass of water adhere to each other.