The ground is the layer used to prepare a support for painting; its colour and tone can affect the chromatic and tonal values of the paint layers applied over it.

When the support is a panel the ground is usually made of gesso, but when the support is canvas the ground is more usually made of underlying paint layers. Sometimes two layers of ground are applied, this is called a 'double ground'. Artists may have individual preferences for coloured grounds: Poussin used reddish grounds, Rembrandt favoured brownish ones.

A white ground was preferred by some19th-century artists, especially the Impressionists.