Marysville is a city in and the county seat of Union County, Ohio, United States. Marysville is part of the metropolitan statistical area of Columbus, Ohio. The population was 22,094 at the 2010 census. This marks a 38.59% increase from 2000. Marysville's longtime slogan is "Where the Grass is Greener". In December 2008, Marysville was designated as a "Preserve America Community" by the White House.