The so-called Sudovian Book (, ) was an anonymous work about the customs, religion, and daily life of the Old Prussians from Sambia. The manuscript was written in German in the 16th century. The original did not survive and the book is known from later copies, transcriptions and publications. Modern scholars disagree on the origin and value of the book. Despite doubts about its reliability, the book became popular and was frequently quoted in other history books. Much of the Prussian mythology is reconstructed based on this work or its derivatives.