An earth lodge is a semi-subterranean building covered partially or completely with earth, best known from the Native American cultures of the Great Plains and Eastern Woodlands. Earth lodges are circular, dome-shaped dwellings with heavy timber superstructures covered by thick layers of earth, typically with a central or slightly offset smoke hole at the apex and a tunnel-like entryway. The type emerged in the early 1500s and persisted into the reservation era of the late 19th century. Tribes most frequently associated with earth-lodge architecture include the Mandan, Hidatsa, Arikara, Pawnee, Otoe, Kansa, Omaha, and Ponca, although several other groups also adopted the style. Earth lodges have also been identified archaeologically at Mississippian culture sites in the southeastern United States.

With diameters of up to 60 feet (18 m), historic-period earth lodges were the largest and most complex structures built on the Plains until the 20th century.

The origins of the earth lodge are not entirely clear, though it was a Northern Plains innovation. Between AD 1000 and 1400, horticultural villagers in the Central Plains built square houses, while Northern Plains villagers constructed rectangular structures. Although these earlier buildings are frequently called earth lodges, they were not true earth lodges; they were vertical-walled structures with thin coverings of wattle and daub or thatch. A few oval to circular structures appeared in northern Nebraska and central South Dakota in the 1400s, but their floor plans do not reflect the fully developed earth-lodge style.

The earliest true earth lodges were built in central North Dakota and northern South Dakota Missouri River villages in the early 1500s by the ancestors of the Mandans and Arikaras. These structures were thicker and more heavily insulated than the earlier dwellings and are thought to have been a response to the cooling temperatures of the Neoboreal ("Little Ice Age") climatic regime. The architectural style subsequently diffused from the upper Missouri as additional sedentary tribes migrated onto the Plains and adopted the form. The Pawnees were established in central Nebraska by 1600 and living in earth-lodge villages; archaeological and ethnohistorical evidence places the Otoes, Omahas, and Poncas in earth-lodge villages on the eastern margins of the Central Plains by 1700. The Cheyenne briefly adopted earth-lodge architecture in the mid-18th century during their occupancy of eastern North Dakota.

Earth-lodge construction began with the excavation of a shallow circular floor pit, typically less than one foot deep, with a diameter varying between 20 and 60 feet (6.1 and 18.3 m). Heavy vertical timbers served as central roof supports: Northern Plains earth lodges almost always had four center posts, while the Pawnees, Omahas, Otoes, and other Central Plains tribes used four, six, eight, ten, or even twelve. The center posts were forked at the top and connected by horizontal beams. A secondary row of shorter posts was set around the perimeter of the floor pit, several feet inside the wall, connected at the top by horizontal cross-stringers. Closely spaced sloping posts then spanned from the top of these stringers to the ground outside the house pit, and rafters extended in spoke-like fashion from the wall stringers to the horizontal beams connecting the center posts, leaving an opening at the center for a smoke hole. Thatching and then layers of thick sod and grass covered the superstructure.

A sloping or vertical-walled entry passage extended from one side of the lodge, typically facing south or east, and could be 6 to 15 feet (1.8 to 4.6 m) in length. The earth covering and partially subterranean foundation provided thermal insulation against the extreme temperature swings of the Plains. The most common construction wood was cottonwood, a soft wood that meant lodges typically required rebuilding every seven to ten years.

Interior features included a central fire basin, one or more deep bell-shaped food storage chambers (narrow at the lodge floor and expanding to three to five feet at their bases, and five to eight feet deep), and altars or sacred areas, typically on the back wall opposite the entrance. The Hidatsa called the space between the outer vertical posts and the exterior leaning posts the atuti; this area was used for beds, firewood, tools, and other personal items. One or more extended families occupied an earth lodge, which could house up to sixty people.

In Hidatsa culture, men raised the large structural logs, but the rest of the construction work was done by women; a lodge was therefore considered to be the property of the woman who built it. Building an earth lodge was considered a sacred task.