Mummy Cave is a rock shelter and archeological site in Park County, Wyoming, United States, near the eastern entrance to Yellowstone National Park. The site is adjacent to the concurrent U.S. Routes 14/16/20, on the left bank of the North Fork of the Shoshone River at an altitude of 6,310 feet (1,920 m).
At its mouth, the cave is approximately 150 feet (46 m) wide, and it extends approximately 40 feet (12 m) into a volcanic cliff above the North Fork. It lies along the left bank of the river, next to the mouth of a small stream and opposite from the mouth of Blackwater Creek. The largest known cave along the North Fork, it is believed to have been carved by the river's flow; the reason for its diversion away from the alcove is unknown.
The wide range of artifacts discovered at the site has caused Mummy Cave to be seen as a highly significant site for the study of Rocky Mountain archeology. The cave's significance was recognized by the National Park Service with its placement on the National Register of Historic Places in 1981.