Westphalia is a city in Osage County, Missouri, United States. The population was 389 at the 2010 census. It is part of the Jefferson City, Missouri Metropolitan Statistical Area. Westphalia is heavily influenced by the German heritage of the majority of its inhabitants. Many of the early settlers of the area came from the Westphalen area of Germany, hence the name. Many buildings are influenced by nineteenth century German architecture, and streets are labeled in both English and German.