Thomas of Monmouth was a monk who lived in a Benedictine monastery in Norwich, in Norfolk, England during the 12th century.
Thomas of Monmouth was the author of The Life and Miracles of William (1173), an anti-semitic polemic which accused the Jews of murdering a young boy whose body was found on Mousehold Heath, Norwich, in 1144.
Monmouth's writing helped William of Norwich inflame anti-semitic sentiment in England, resulting in the eventual expulsion of the Jews from England in 1290.