Neihart is a town in Cascade County, Montana, United States. It is located in the center of Little Belt Mountains. The population was 51 at the 2010 census. It is part of the Great Falls, Montana, Metropolitan Statistical Area. It is one of only three places in the world where Neihart quartzite—reddish, coarse-grained sandstone with interbedded dark-green sandstone and shale—may be found (the town gives the mineral its name).
The town has a total area of 1.99 square miles (5.15 km2), all of it land. Its elevation is 5,661 feet (1,725 m).
The Neihart area is rich in mineral deposits. Gold, lead, sapphires, silver, and zinc have all been discovered and mined in the area. Much of the exposed rock in the area is dated to the Precambrian era, or around or before 542 million BC. Rocks in the area belong to what is known as the Belt Supergroup and rest against granitic gneiss. Amethyst and marine fossils are common in the area. Pinto diorite, a red-and-green spotted diorite, is found in large quantities in the area.
Neihart is on U.S. Route 89, also known as the Kings Hill Scenic Byway.