The Royal Prayer Book (London, British Library Royal MS 2.A.XX) is a collection of prayers believed to have been copied in the late eighth century or the early ninth century. It was written in West Mercia, likely either in or around Worcester. Folio 45v contains what seems to be the first manuscript attestation in any Germanic language of the common noun elf. The manuscript also contains detailed Old English glosses from the tenth century in the Mercian dialect of Old English.