Arnold is a census-designated place (CDP) in Rice Lake Township, Saint Louis County, Minnesota, United States. The population was 2,960 at the 2010 census. The census-designated place of Arnold is located entirely within Rice Lake Township, adjacent to the north side of the city of Duluth.
The name "Arnold", as a place of residence, is seldom used today by the younger generations. Since circa 1970, those who reside in this area identify themselves as residents of "Rice Lake" (Rice Lake Township) or Duluth. In the present day, the CDP name "Arnold" is used only for statistical purposes for the U.S. decennial census count of population.