Lost artworks are original pieces of art that credible sources indicate once existed but that cannot be accounted for in museums or private collections or are known to have been destroyed deliberately or accidentally, or neglected through ignorance and lack of connoisseurship.
The US FBI maintains a list of "Top Ten Art Crimes"; a 2006 book by Simon Houpt and several other media outlets have profiled the most significant outstanding losses.
Portrait of a Young Man by Raphael
Nativity with San Lorenzo and San Francesco by Caravaggio Est. (2006) $20,000,000 USD
Storm on the Sea of Galilee by Rembrandt Est. (2006) priceless
Landscape with an Obelisk by Govert Flinck Est. (2006) priceless
The Concert by Vermeer Est. $20,000,000–priceless
Alexander III Commemorative egg by Fabergé Est. $20–30,000,000
Royal Danish egg (Danish Jubilee egg) by Fabergé Est. $20–30,000,000
Vase with Lychnis by Van Gogh
Chez Tortoni by Édouard Manet Est. (2006) priceless
White Duck by Jean-Baptiste Oudry Est. (2006) $8,800,000 USD
View of Auvers-sur-Oise by Cézanne Est. (2006) $3,000,000 USD