Gold ground (both a noun and adjective) or gold-ground (adjective) is a term in art history for a style of images with all or most of the background in a solid gold colour. Historically, real gold leaf has normally been used, giving a luxurious appearance. The style has been used in several periods and places, but is especially associated with Byzantine and medieval art in mosaic, illuminated manuscripts and panel paintings, where it was for many centuries the dominant style for some types of images, such as icons. For three-dimensional objects, the term is gilded or gold-plated.

Gold in mosaic began in Roman mosaics around the 1st century AD, and originally was used for details and had no particular religious connotation, but in Early Christian art it came to be regarded as very suitable for representing Christian religious figures, highlighting them against a plain but glistering background that might be read as representing heaven, or a less specific spiritual plane. Full-length figures often stand on more naturalistically coloured ground, with the sky in gold, but some are shown fully surrounded by gold. The style could not be used in fresco, but was adapted very successfully for miniatures in manuscripts and the increasingly important portable icons on wood. In all of these the style required a good deal of extra skilled work, but because of the extreme thinness of the gold leaf used, the cost of the gold bullion used was relatively low; lapis lazuli blue seems to have been at least as expensive to use.

The style remains in use for Eastern Orthodox icons to the present day, but in Western Europe fell from popularity in the Late Middle Ages, as painters developed landscape backgrounds. Gold leaf remained very common on the frames of paintings. There were pockets of revivalist use thereafter, as for example in Gustav Klimt's so-called "Golden period". It was also used in Japanese painting and Tibetan art, and sometimes in Persian miniatures and at least for borders in Mughal miniatures.

Writing in 1984, Otto Pächt said "the history of the colour gold in the Middle Ages forms an important chapter which has yet to be written", a gap which perhaps has still only been partly filled. Apart from large gold backgrounds, another aspect was chrysography or "golden highlighting", the use of gold lines in images to define and highlight features such as the folds of clothing. The term is often extended to include gold lettering and linear ornamentation.

Recent scholarship has explored the effects of gold ground art, especially in Byzantine art, where the gold is best understood as representing light. Byzantine theology was interested in light, and could distinguish several different kinds of it. The New Testament and patristic accounts of the Transfiguration of Christ were an especial focus of analysis, as Jesus is described as emitting or at least bathed in a special light, whose nature was discussed by theologians. Unlike the main late medieval theory of optics in the West, where the viewer's eye was believed to emit rays that reached the viewed object, Byzantium believed the light proceeded from the object to the viewer's eye, and Byzantine art was very sensitive to alterations in the light conditions in which art was seen.

Otto Pächt wrote that "medieval gold ground was always interpreted as a symbol of transcendental light. In the light transmitted by the gold of Byzantine mosaics there was eternal cosmic space dissolved at its most palpable in the unreal, or even, in the supernatural; and yet our senses are directly touched by this light."

According to one scholar, "in a gold ground painting, the sacred image the Virgin, for example  was firmly located on the material surface of the picture plane. She was, in this way, real, and the painting as much presented the Madonna as represented her ... [gold ground paintings] ...which blurred the distinction between the subject and its representation, were considered to have a physical and psychological presence like that of a real person."

In mosaics the figures and other areas in colours were normally added first, then the gold placed around them. In painting the opposite sequence was used, with the figures "reserved" around their outline in the underdrawing.