De Situ Britanniae

De Situ Britanniae (The Description of Britain) is a fictional description of the peoples and places of ancient Britain. Purported to contain the account of a Roman general preserved in the manuscript of a fourteenth century English monk, it was considered the premier source of information on Roman Britain for more than a century after it was made available in 1749.

The forgery was created by Charles Bertram, an eighteenth-century Englishman then living in Copenhagen. He first disclosed the existence of De Situ Britanniae in 1747 and made his copy of it available in London in 1749, where it was kept in the Arundel Library of the Royal Society. The work was published by Bertram in 1757. De Situ Britanniae was not debunked as a forgery until the middle of the nineteenth century, by which time its misinformation had been incorporated into many respected publications of ancient British history.