Erode District (previously known as Periyar District) is a district in the Kongu Nadu region (western part) of the state of Tamil Nadu, India. It was the largest district by area in the state before the Formation of Tirupur District and the headquarters of the district is Erode. It is divided into two revenue divisions namely Erode and Gobichettipalayam and further subdivided into 6 taluks. Periyar district was a part of Coimbatore District before its bifurcation on September 17, 1979 and was renamed as Erode District in 1996. As of 2011, the district had a population of 2,251,744 with a sex-ratio of 993 females for every 1,000 males, much above the national average of 929.
The region belonging to the present day districts were ruled successively by several dynasties of South India including the Cheras, Cholas and Pandyas. It was under the rule of Cheras in the first millennium and various Karnataka rulers. During the 10th to 12th centuries the region was part of the larger Chola Empire .
The region became part of Vijayanagara empire in 1300's, later under Nayaks of Madurai until 17th century. Under the Madurai Nayaks, the Polygar system of administration was established, who were the Governors of the region. Since mid 17th century the region was part of Kingdom of Mysore but continuing the Polygar system of administration.
The Polygar cheiftain Dheeran Chinnamalai was one of the governors of the region, who played a major part in the early struggle for Indian Independence in the Polygar Wars against the British East India Company. After the Polygar and Mysore wars in the late 18th century, the area came under control of the British until the Indian Independence in 1947. It was a part of the erstwhile Coimbatore district until its bifurcation in 1979.