Vandalia is a city in Montgomery County, Ohio, United States, and a suburb of Dayton. Its population was 15,246 during the 2010 census. In addition to being the city closest to Dayton International Airport, Vandalia lies at the crossroads of I-75 and I-70, making it a major hub for business.Vandalia is a sister city to Lichtenfels, Germany, and Prestwick, Scotland. It is part of the Dayton Metropolitan Statistical Area.