Ah-Shi-Sle-Pah Wilderness is a protected desert landscape in northwestern New Mexico between Chaco Canyon and the De-Na-Zin Wilderness, known for multicolored badlands, sandstone hoodoos, petrified wood, and exposed dinosaur remains. First designated a Bureau of Land Management Wilderness Study Area in May 1992, it gained permanent federal protection on March 12, 2019, as part of the National Wilderness Preservation System. Its late Cretaceous rocks, including parts of the Fruitland and Kirtland formations, preserve an important paleontological record. Work here has produced the type specimen of Pentaceratops fenestratus and fossils later used to identify Ahshislepelta minor.