Dystrophaeus is the name given to an extinct genus of eusauropod dinosaur from the early Kimmeridgian stage of the Late Jurassic that existed around 155.7 Ma. Its fossils were found in the Tidwell Member of the Morrison Formation of Utah. Its estimated mass is 12 tonnes (13 short tons). Finally, a modern analysis by David Gillette concluded it was a member of the Diplodocidae. However, many researchers consider the taxon to be a nomen dubium.