Smithville is a city in DeKalb County, Tennessee, United States.

Tennessee State Route 56 (Congress Boulevard) crosses US 70 a few blocks southeast of the center of town and leads north 13 miles (21 km) to Interstate 40 at Silver Point and 19 miles (31 km) south to McMinnville.

[13] According to the United States Census Bureau, the city has a total area of 5.9 square miles (15.3 km2), all land.

[7] As of the 2020 United States census, there were 5,004 people, 1,631 households, and 1,090 families residing in the city.

Smithville is referred to by a local-boy Marine talking to a girl and pointing to labels on a map during a dance hall scene, 17 minutes into the 1949 World War II John Wayne film, Sands of Iwo Jima, where it is mentioned, apart from everybody in his family being related to much of Tennessee, as being famous for "corn tobacco" and "more fertilizer than any other place in the world".

Joe L. Evins helped start the world-famous Smithville Fiddler's Jamboree & Crafts Festival.