The Vanni chieftaincies or Vanni tribes was a region between Anuradhapura and Jaffna, but also extending to along the eastern coast to Panama and Yala, during the Transitional and Kandyan periods of Sri Lanka. The heavily forested land was a collection of chieftaincies of principalities that were a collective buffer zone between the Jaffna Kingdom, in the north of Sri Lanka, and the Sinhalese kingdoms in the south. Traditionally the forest regions were ruled by Vedda rulers. Later on, the emergence of these chieftaincies was a direct result of the breakdown of central authority and the collapse of the Kingdom of Polonnaruwa in the 13th century, as well as the establishment of the Jaffna Kingdom in the Jaffna Peninsula. Control of this area was taken over by dispossessed Sinhalese nobles and chiefs of the South Indian military of Māgha of Kalinga (1215–1236), whose 1215 invasion of Polonnaruwa led to the kingdom's downfall. Sinhalese chieftaincies would lay on the northern border of the Sinhalese kingdom while the Tamil chieftaincies would border the Jaffna Kingdom and the remoter areas of the eastern coast, north western coast outside of the control of either kingdom.
The chieftains, who were known as Vanniars, would function like feudal lords in their territories. During much of the Transitional period when the island was politically unstable, depending on the situation at the time, the chieftains would owe their allegiance to one or the other kingdom. They offered military protection to those who came under their authority. Vanniars referred to a broad category of people who could have been appointees of the Sinhalese kings, who administered outlying districts or autonomous rulers of large, sparsely populated and undeveloped lands. The Vanniars in general paid tribute to the Kingdom of Kotte and later to the Kingdom of Kandy, apart from Confederation of Northern Tamil Vanniars paid tribute to the Jaffna Kingdom until it collapsed.