This chapter contends that forgery should be considered a form of historical writing. It presents evidence to show that, in the Middle Ages, forgeries not only frequently constituted significant parts of archives and other resources for the writing of history, but that forgeries themselves were often the products of historical research on the part of their authors. If forgeries are considered one end of a spectrum of historical writing (rather than the binary opposite of the true historical document) then a nuanced understanding of the relationships between forgeries and genres such as hagiography and the medieval chronicle becomes possible. After discussion of these relationships, the chapter concludes with an examination of the criticism of forgeries during the Middle Ages. Forgeries were often denounced; yet they could also survive denunciation, not because of a lack of critical sense on the part of medieval audiences, but because of the importance of their function as historical writing.