The Mag Mell Ruins (English dub: /ˈmæɡ mɛl/) is a landmark in Xenoblade Chronicles. It is located on the ground floor of Tephra Cave. Shulk, Reyn, and Fiora pass through here when they are going to collect the Ether Cylinders, and Shulk and Reyn pass through again on their way to Bionis' Leg. Defence Force soldiers can be found inside.
In a short story included in Xenoblade: The Secret File it is revealed to be part of an ancient Alcamoth trading ship used for transporting Ether Cylinders. It is also a training ground for the Defence Force.