Fulton County is a county in the north-central portion of the U.S. state of Georgia. As of the 2020 United States census, the population was 1,066,710, making it the state's most populous county. Its county seat and most populous city is Atlanta, the state capital. About 90% of the city of Atlanta is within Fulton County; the remaining portion is in DeKalb County. Fulton County is the principal county of the Atlanta–Sandy Springs–Roswell metropolitan statistical area.