Lost artworks are original pieces of art that credible sources or material evidence indicate once existed but that cannot be accounted for in museums or private collections, as well as works known to have been destroyed deliberately or accidentally or neglected through ignorance and lack of connoisseurship.

The Art Loss Register is a commercial computerized international database which captures information about lost and stolen art, antiques and collectables. It is operated by a commercial company based in London.

In the U.S., the FBI maintains the National Stolen Art File, "a database of stolen art and cultural property. Stolen objects are submitted for entry to the NSAF by law enforcement agencies in the U.S. and abroad."

A number of search and recovery efforts were created in response to major loss events, notably:

This section lists articles or article sections on lost works.