Vandalia is a city in Montgomery County, Ohio, United States. It is located in the southwest part of the state, just north of Dayton. The city covers a total area of approximately 12 square miles and has a population of around 15,246 people as of the 2010 census. Vandalia is known for its rich history, diverse community, and convenient access to major highways and airports. The city offers various amenities and recreational opportunities for its residents, including parks, hiking and biking trails, community events, and shopping centers.