Photomontage is the process (and result) of making a composite picture by cutting and joining a number of photographs. The English photographer, Henry Peach Robinson (1830-1901) is credited with making the first photomontages, soon after starting his career in 1857.
Many of the early examples of fine-art photomontage superimposed photographed elements on watercolours, a combination returned to by (e.g.) George Grosz, in about 1915. David Ridge has extended this idea by using photographs of painted, sculptured landscapes as part of the composition (1999/2000). Other methods for combining pictures are also called photomontage, such as combination printing (the printing from more than one negative on a single piece of printing paper - e.g. O. G. Rejlander, 1857) and front-projection and computer montage techniques.
See also Hag (b.1949), John Heartfield