Sandpaper, also known as coated abrasive or emery paper, is a type of material that consists of sheets of paper or cloth with an abrasive substance glued to one face. In the modern manufacture of these products, sand and glass have been replaced by other abrasives such as aluminium oxide or silicon carbide. It is common to use the name of the abrasive when describing the paper, e.g. "aluminium oxide paper", or "silicon carbide paper".

There are many varieties of sandpaper, with variations in the paper or backing, the material used for the grit, grit size, and the bond.

Sandpaper is produced in a range of grit sizes and is used to remove material from surfaces, whether to make them smoother (for example, in painting and wood finishing), to remove a layer of material (such as old paint), or sometimes to make the surface rougher (for example, as a preparation for gluing). The grit size of sandpaper is usually stated as a number that is inversely related to the particle size. A small number such as 20 or 40 indicates a coarse grit, while a large number such as 1500 indicates a fine grit.

The first recorded instance of sandpaper was in 13th-century China when crushed shells, seeds, and sand were bonded to parchment using natural gum.

Shark skin (placoid scales) has also been used as an abrasive, and the rough scales of the Coelacanth are used for the same purpose by the natives of Comoros. Boiled and dried, the rough horsetail plant is used in Japan as a traditional polishing material, finer than sandpaper.

Cheap sandpaper was often passed off as glass paper; Stalker and Parker cautioned against it in A Treatise of Japaning and Varnishing published in 1688.

Glass paper was manufactured in London in 1833 by John Oakey, whose company had developed new adhesive techniques and processes, enabling mass production. Glass frit has sharp-edged particles and cuts well whereas sand grains are smoothed down and do not work well as an abrasive.

In the United States, a major development in the history of coated abrasives was the work of Henry Hudson Barton. After emigrating from England in 1846, Barton married into a Philadelphia sandpaper manufacturing family. Drawing on his knowledge of gem minerals, he began experimenting with Adirondack garnet as an abrasive. Barton went on to establish mining operations at Gore Mountain (New York), in 1878, creating what became the world’s oldest continuously operating garnet mine. Garnet from Barton Mines was widely adopted in coated abrasives and further developments in sandpaper and remains a significant abrasive mineral today.