Greeneville is a town in and the county seat of Greene County, Tennessee, United States. The population as of the 2020 census was 15,479. The town was named in honor of Revolutionary War hero Nathanael Greene, and it is the second oldest town in Tennessee. It is the only town with this spelling in the United States, although there are numerous U.S. towns named Greenville. The town was the capital of the short-lived State of Franklin in the 18th-century history of East Tennessee.

Greeneville is known as the town where United States President Andrew Johnson began his political career when elected from his trade as a tailor. He and his family lived there for most of his adult years. It was an area of strong abolitionist and Unionist views and yeoman farmers, an environment that influenced Johnson's outlook.

The Greeneville Historic District was established in 1974.

The U.S. Navy Los Angeles-class submarine USS Greeneville was named in honor of the town.

Greeneville is part of the Johnson City-Kingsport- Bristol TN-VA Combined Statistical Area – commonly known as the "Tri-Cities" region.
From 1947 to 2005, Magnavox—an electronics manufacturer best known for its television sets—operated its main three facilities in Greeneville. Magnavox was at one time the largest employer of Greeneville, employing more than 5,000 workers. Eight years after the first plant opened, Magnavox workers voted to form a union through the IBEW. In 1974, the facilities and the Magnavox company were acquired by the electronics giant Philips. Throughout the 1980s and early 1990s, the Greeneville facility saw a fluctuation and drops in employment. In 1997, Phillips sold its facilities to Knoxville-based company Five Rivers Electronic Innovations. In 2005, Five Rivers closed the former Magnavox plant after declaring bankruptcy. Before its shuttering, the Five Rivers facility was the site of the last television manufactured in the United States, which is now on display in the Greeneville-Greene County History Museum.