Polk County is a county located in the southeastern corner of the U.S. state of Tennessee. As of the 2020 United States census, its population was 17,544. Its county seat is Benton. The county was created on November 28, 1839, from parts of Bradley and McMinn counties, after final removal of most Cherokee from the region that year. The county was named after then-governor (and future president) James K. Polk. Polk County is included in the Cleveland, Tennessee Metropolitan Area Statistical Area, which is also included in the Chattanooga–Cleveland–Dalton, TN–GA–AL Combined Statistical Area.

Prior to the settlement of the Europeans, Polk County was inhabited by the Cherokee, and before them, thousands of years of indigenous cultures. The portion of Polk County north of the Hiwassee River was ceded by the Cherokee Nation to the US in the Calhoun Treaty of 1819. The rest of the county was part of the Ocoee District. The Cherokee were forcibly removed from here in 1838-1839 and taken to Indian Territory, in a passage that became known as the Trail of Tears.

Polk County was created by an act of the Tennessee General Assembly on November 23, 1839. The location for the county seat of Benton was chosen by an election held on February 4, 1840.

Copper was discovered in Ducktown in 1843. By the 1850s, a large mining operation was underway in southeastern Polk County; the area became known as the Copper Basin. This operation continued until 1987, when the last mine closed.

During the Civil War, Polk County was one of only six counties in East Tennessee to support the Confederacy, voting in favor of Tennessee's ordinance of secession in June 1861. During the war, the copper mines supplied about 90% of the Confederacy's copper; their capture by Union forces after the Confederate defeat at the Battles for Chattanooga in November 1863 proved a major blow to the Confederacy. On November 29, 1864, a series of raids by Confederate bushwhacker John P. Gatewood in Polk County resulted in at least 16 deaths.

US-64 through the Ocoee Gorge was built around 1926. It was not paved until the 1940s. The East Tennessee Power Company, later the Tennessee Electric Power Company (TEPCO), constructed two hydroelectric dams on the Ocoee River, Ocoee Dams 1 and 2, which were completed in 1911 and 1913, respectively. TEPCO was later purchased by the Tennessee Valley Authority (TVA), founded in 1933. It constructed an additional dam on this river, Ocoee Dam No. 3, completed in 1943, as well as the powerhouse for Apalachia Dam on the Hiwassee River in northern Polk County, which was also completed in 1943.

In 1973, a large music festival known as the "Midwest Monster Peace Jubilee and Music Festival", commonly known as the "Monster Peace Jubilee", was planned by Indiana-based promoter C.F. Manifest Inc. to take place on a 1,300-acre farm north of Benton on Labor Day of that year. The farm was owned by the county executive. (It has been redeveloped as the Chilhowee Gliderport.) Nicknamed "Polkstock" due to its resemblance to 1969's Woodstock in Bethel, New York, the event was expected to attract approximately 500,000 people. Locals strongly opposed it, especially members of the religious communities, who believed the festival would bring much of the perceived rock music culture. The festival was eventually halted by the state circuit court, on the request of the district attorney, who said that the festival would constitute a public nuisance, due to drug, health, and traffic problems.

On May 27, 1983, a massive explosion at a secret illegal fireworks factory killed eleven workers. The operation, located on a bait farm a few miles south of Benton, was unlicensed. It produced M-80 and M-100 fireworks, both illegal, and was the largest illegal fireworks operation in the United States to date.