Obsidian Cliff, also known as 48YE433, was an important source of lithic materials for prehistoric peoples in Yellowstone National Park near Gardiner, Montana. The cliff was named by Philetus Norris, the second park superintendent in 1878.
It was declared a National Historic Landmark in 1996.
It is located about 13 miles (21 km) south of Mammoth Hot Springs, on the east side of the Mammoth-Norris section of the Grand Loop Road. The Obsidian Cliff Kiosk, just north, is also listed on the National Register. Obsidian Cliff is also located on the northern end of Beaver Lake in Yellow Stone National Park.