A province of Ceylon, identified with the modern Jaffna peninsula and the north west of Ceylon.
The Buddha's second visit to Ceylon was to Nāgadīpa, to settle a dispute between two Nāgas, Mahodara and Cūlodara (Mhv.i.47).
Jambukola (q.v.) was a harbour in Nāgadīpa, and there a vihāra was built by Devānampiyatissa (Ibid., xx.25) and later restored by Kanitthatissa (Ibid., xxxvi.9). This vihāra was probably called Tissa vihāra (See ibid.,36).
Another vihāra, called Sālipabbata, was built by Mahallaka Nāga (Ibid.,xxxv.124). The Unnalomaghara, the Rājāyatana dhātucetiya and the Amalacetiya were probably all places of worship in Nāgadīpa (Cv.xlii.62).
The Valāhassa Jātaka (J.ii.128) says that the coast of Ceylon, from the river Kalyānī to Nāgadīpa, was once infested by yakkhinis. Once (J.iii.187) Nāgadīpa was known as Serumadīpa, and near by was Karadīpa, earlier known as Ahidīpa (J.iv.238).
An old story, given in the Commentaries (E.g., VibhA.444), speaks of a king called Dīparāgā, who reigned over Nāgadīpa in great splendour. Nāgadīpa was once an important centre of Buddhism in Ceylon (E.g., ibid., 446, 467; AA.i.422. MA.i.545; see also J.R.A.S., vol. xxvi) and contained many places of pilgrimage. There is a legend (DA.iii.899; VibhA.433) which relates that, when the Buddha's sāsana comes to an end, all the Buddha's relics in Ceylon will gather together at the Mahācetiya and travel to the Rājāyatanacetiya in Nāgadīpa, and then from there to the Mahābodhi tree at Gayā.
According to the Rasavāhinī (ii.19) the place was so called because it was given as gift to the woman named Nagā. See Nāgā (7).