Smithfield is a town in Johnston County, North Carolina, United States. In 2008, the estimated population was 12,965. It is the county seat of Johnston County. The city is home to the Ava Gardner Museum.
Smithfield is located at 35°30′33″N 78°20′47″W / 35.50917°N 78.34639°W / 35.50917; -78.34639 (35.509129, -78.346456).
According to the United States Census Bureau, the town has a total area of 11.4 square miles (29.6 km²), of which 11.4 square miles (29.6 km²) is land and 0.09% is water.