Medicine Rocks State Park, State park in Carter County, Montana, US.

Medicine Rocks State Park is a natural area in southeastern Montana built around a collection of sandstone pillars that rise well above the surrounding grassland. The rock formations are riddled with hollows, passages, and niches shaped by wind and water over millions of years.

Medicine Rocks was part of the working 101 Ranch of the Standard Cattle Company from 1888, and cowboys carved their names into the soft sandstone. Carter County seized the land in the 1930s for unpaid taxes and transferred it to Montana in February 1957; the state park was established in 1965. It was listed on the National Register of Historic Places in 2017 and became a certified International Dark Sky Sanctuary in 2020.

The Crow called the site Inyan-oka-lo-ka, "rock with a hole in it", and each year made offerings of beads, paint or tobacco to the "Little People" they believed lived among the rocks. They also built stone "fasting beds" where they lay seeking visions. Tribes including the Arikara, Assiniboine, Mandan, Cheyenne and Sioux used the rocks as lookout, storage place and camp.

The park lies 11 miles north of Ekalaka and about 25 miles west-southwest of Baker, reached by gravel roads. Camping is basic, with tables and fire rings; the ground is open prairie, so bring water and sun protection. In 1990 the state tried to close the park at night, but after 240 people protested in Baker it stayed open.

The sandstone here formed around 61 million years ago from ancient river deposits, and fossils of early mammal ancestors and extinct snakes from the Paleocene epoch have been found within it. This makes the site one of the few places where you can stand among rocks that date back to the first chapter of mammal life on Earth.