An art museum, or art gallery, is an organization, usually with buildings or spaces for the display of art from the museum's own collection. It might be in public or private ownership, be accessible to all, or have restrictions in place. Although primarily concerned with visual art, art museums are often used as a venue for other cultural exchanges and artistic activities, such as lectures, jewelry, performance arts, music concerts, or poetry readings. Art museums also frequently host themed temporary exhibitions, which often include items on loan from other collections.

An institution dedicated to the display of art can be called an art museum or an art gallery, and the two terms may be used interchangeably. This is reflected in the names of institutions around the world, some of which are considered art galleries, such as the National Gallery in London and Neue Nationalgalerie in Berlin, and some of which are considered museums, including the Metropolitan Museum of Art and the Museum of Modern Art in New York City and the National Museum of Western Art in Tokyo.

The phrase "art gallery" is also sometimes used to describe businesses which display art for sale, but these are not art museums.

Throughout history, large and expensive works of art have generally been commissioned by religious institutions or political leaders and been displayed in temples, churches, and palaces. Although these collections of art were not open to the general public, they were often made available for viewing for a section of the public. In classical times, religious institutions began to function as an early form of art gallery. Wealthy Roman collectors of engraved gems and other precious objects, such as Julius Caesar, often donated their collections to temples. It is unclear how easy it was in practice for the public to view these items.

In Europe, from the Late Medieval period onwards, areas in royal palaces, castles, and large country houses of the social elite were often made partially accessible to sections of the public, where art collections could be viewed. At the Palace of Versailles, entrance was restricted to people of certain social classes who were required to wear the proper apparel, which typically included the appropriate accessories, silver shoe buckles and a sword, could be hired from shops outside. The treasuries of cathedrals and large churches, or parts of them, were often set out for public display and veneration. Many of the grander English country houses could be toured by the respectable for a tip to the housekeeper, during the long periods when the family were not in residence.

Special arrangements were made to allow the public to see many royal or private collections placed in galleries, as with most of the paintings of the Orleans Collection, which were housed in a wing of the Palais-Royal in Paris and could be visited for most of the 18th century. In Italy, the art tourism of the Grand Tour became a major industry from the 18th century onwards, and cities made efforts to make their key works accessible. The Capitoline Museums began in 1471 with a donation of classical sculpture to the city of Rome by the Papacy, while the Vatican Museums, whose collections are still owned by the Pope, trace their foundation to 1506, when the recently discovered Laocoön and His Sons was put on public display. A series of museums on different subjects were opened over subsequent centuries, and many of the buildings of the Vatican were purpose-built as galleries. An early royal treasury opened to the public was the Green Vault of the Kingdom of Saxony in the 1720s.

Privately funded museums open to the public began to be established from the 17th century onwards, often based around a collection of the cabinet of curiosities type. The first such museum was the Ashmolean Museum in Oxford, opened in 1683 to house and display the artefacts of Elias Ashmole that were given to Oxford University in a bequest.

The Kunstmuseum Basel, through its lineage which extends back to the Amerbach Cabinet, which included a collection of works by Hans Holbein the Younger and purchased by the city of Basel in 1661, is considered to be the first museum of art open to the public in the world.