Harmon is a census-designated place (CDP) and unincorporated community in Morton County, North Dakota, United States. It is north of Mandan and northwest of Bismarck, the state capital. Harmon's population was 259 as of the 2020 census.
The town was sited on July 23, 1913, by Willis T. McConnell and named for two bachelor brothers, George and H.H. Harmon. The town went into decline during the Depression in the 1930s and virtually disappeared. The original cemetery is still in use. On January 15, 1951, two Northern Pacific freight trains collided outside of town. The town has repopulated in the 20th century.
Harmon is east of North Dakota Highway 1806, north of Mandan. The original townsite is along the western edge of the Missouri River floodplain, with current development sited in the western part of the CDP, above the river bluffs. Harmon Lake Recreation Area is on the west side of Highway 1806, on a reservoir built on Otter Creek, a tributary of the Missouri.
Harmon is within the Mandan Public Schools district.