The Nibelungenlied is a heroic epic surpassed only by the Iliad of Homer. It was written at about A.D. 1200 by an unnamed poet, for performance at court in Austria somewhere between Vienna and Passau. In it there culminated a tradition of heroic poetry reaching back to the sixth or fifth century A.D. in the lands of the Germanic peoples, and so well did it succeed in its own age that, for want of copying, all earlier poems on the theme in German were lost for ever. Modern poet and poetasters have often returned to its subject, prominent among them Richard Wagner with his gigantic music drama Der Ring des Nibelungen with which (as with his Parsifal and his Tristan -- whatever their merits as modern works of art) he has unfortunately harmed the cause of medieval German poetry by intruding reckless distortions between us and an ancient masterpiece. Thus those who come to the Nibelungenlied from Wagner will be much surprised by what they read in it.
-- Arthur Thomas Hatto, 1965; introduction to his prose translation of the Nibelungenlied