The Nisi (or Nishi, Nissi, Nyishi, Nyising) people principally inhabit the Indian state of Arunachal Pradesh. Known as the Nyishi (alternative spelling Nyisi meaning 'people of the land or the human being'). They inhabit the Papum Pare, East Kameng and Lower Subansiri, Kurung Kumey, parts of upper Subansiri districts of Arunachal Pradesh, as well as the Darrang District and North Lakhimpur district of Assam. Their population of around 300,000 makes them the most populous tribes of Arunachal Pradesh, seconded by the combined tribes of the Adis and the Galongs (Abors) who were the most populous in the 2001 census. The Nyishi language belongs to the Sino-Tibetan family, however, the origin is disputed and no single concrete theory stands unchallenged.

Most Nyishi do not like the idea of intermarriage with other neighboring tribes, which also is common about the other tribes. Polygyny is prevalent among the Nyishi. It signifies ones social status and economical stability and also proves handy during hard times like clan wars or social huntings and other social activities. This institution, however is being challenged. They trace their descent patrilineally and are divided into several clans.