Newtonia is a village in Newton County, Missouri, United States. The population was 199 at the 2010 census. It is part of the Joplin, Missouri Metropolitan Statistical Area. Newtonia was the site of the Battles of Newtonia. Newtonia has some Antebellum houses, such as the Ritchey Mansion, as well as a cemetery for Civil War dead. It is a farming community and is immediately adjacent to Stark City, Missouri.