Dublin is a city in the U.S. state of Ohio. A suburb of Columbus, it falls within the jurisdictions of Franklin, Delaware, and Union counties. Th…Dublin is a city in the U.S. state of Ohio. A suburb of Columbus, it falls within the jurisdictions of Franklin, Delaware, and Union counties. The population was 49,328 at the 2020 census. Dublin has the highest concentration of Asians of any Ohio city. The Dublin Irish Festival advertises itself as the largest three-day Irish festival in the world.