In Irish mythology, Naisi, Noíse or Noisiu was the nephew of King Conchobar mac Nessa of Ulster, and a son of Uisneach. He is mentioned in the tale known as the Tragic Tale of the Sons of Uisnech, or Exiles of the Sons of Uisnech, usually found within the set of stories in the Táin Bó Cúailnge, part of the Ulster Cycle.

The Hill of Uisneach or Ushnagh is a hill and ancient ceremonial site in the barony of Rathconrath in County Westmeath, Ireland. It is a protected national monument. It consists of numerous monuments and earthworks—prehistoric and medieval—including a probable megalithic tomb, burial mounds, enclosures, standing stones, holy wells and a medieval road. Uisneach is near the geographical centre of Ireland, and in Irish mythology it is deemed to be the symbolic and sacred centre of the island. It was said to be the burial place of the mythical Tuatha Dé Danann, and a place of assembly associated with the druids and the festival of Bealtaine.