Deposition, also known as sedimentation, is the geological process whereby material is added to a landform. This is the process by which wind, water, or ice create a sediment deposit through the laying down of granular material that has been eroded and transported from another geographical location.

Deposition occurs when the forces responsible for sediment transportation are no longer sufficient to overcome forces of particle weight and friction that resist motion. Deposition can also refer to the build up of a sediment from organically derived matter or chemical processes. For example, chalk is made up partly of the microscopic calcium carbonate skeletons of marine plankton, the deposition of which have induced chemical processes to deposit further calcium carbonate.