Interior decoration is the art of decorating a room so it looks good, is easy to use, and functions well with the existing architecture. The goal of interior decoration is to provide a certain "feel" for the room; it encompasses applying wallpaper, painting walls and other surfaces, choosing furniture and fittings, such as light fixtures, and providing other decorations for the area such as paintings and sculptures.

Interior decorating is done professionally by interior designers or interior decorators, and by some architects. It is considered a design field.

There is sometimes a distinction made between interior decorating and interior design. Interior decorating is generally focused more on finishes, such as wallpaper, paint, window coverings, and furnishings. Interior design tends to be more integrated with the architecture, and in addition to the above areas, might also be involved in cabinet making, room layout, window placement, appliance selection, tile and floor selection, and so on.

The role of the interior decorator evolved in the 18th century from the Parisian marchand-mercier and the upholder in London. In Paris, the gild system that had evolved since the late Middle Ages prohibited a craftsman from working with a material with which they had not undergone a formal apprenticeship. Only a marchand-mercier (a "merchant of goods") could fit Chinese porcelains with gilt-bronze handles and mounts, combine Japanese lacquer or Sevres porcelain plaques with marquetry and gilt-bronze mounts on furniture. An early marchand-mercier Gersaint, had his shop-sign painted by Watteau. The Rococo interior was taken out of the hands of the architect and the painter and put in charge of the marchand-mercier.

In London, a parallel is the rise of the "upholder," a member of the London Upholders' Company who increased his design competence from providing upholstery and textiles and the fittings for funerals, to become responsible for the management of the entire interior. In the great London furniture-making partnerships, a cabinet-maker is usually paired with an upholder: Vile and Cobb, Ince and Mayhew, Chippendale and Rannie or Haig.

Palladian architects like William Kent or Matthew Brettingham might provide designs for walls that would be executed by joiners, stuccoists, painters and upholders but often their designs were limited to mantelpieces and monumental side tables, which were considered part of the immovable decor. The neoclassical architect Robert Adam was prepared to design every detail of his interiors if the client wanted, down to the doorknobs and fire-irons. Sir William Chambers designs for furnishings are often underestimated. James Wyatt 's designs for furniture were gathered into an album, perhaps in preparation for an engraved publication. The French marchand-mercier Dominique Daguerre moved to London in 1788 and was responsible for interiors for the Prince Regent and worked with the architect Henry Holland.

In the 1830s, interior decorators were responsible for the revival of interest in Gothic and Rococo styles in England. By the later 19th century, some firms set themselves apart as "art furnishers"

Modern interior decorators began with Lenygon and Morant in London, Jeanselme in Paris, and Ogden Codman in New York.

See also: feng shui