Wallpaper is a kind of material used to cover and decorate the interior walls of homes, offices, and other buildings; it is one aspect of interior decoration. They are usually sold in rolls and are put onto a wall using wallpaper paste. Wallpapers can come either plain (so that it can be painted), or with patterned graphics.

Wallpaper printing techniques include surface printing, gravure printing, silk screen-printing, and rotary printing. Mathematically speaking, there are seventeen basic patterns, described as wallpaper groups, that can be used to tile an infinite plane. All manufactured wallpaper patterns are based on these groups. A single pattern can be issued in several different colorways.

"Wallpaper" is also a term for computer wallpaper.