Nairi (Armenian: Նայիրի, Nayiri or Նաիրի, Nairi; Akkadian: 𒆳𒆳𒈾𒄿𒊑, romanized: mātāt [KUR.KUR] Na-i-ri, lit. 'Nairi lands', also Na-'i-ru) was the Akkadian name for a region inhabited by a particular group (possibly a confederation or league) of tribal principalities in the Armenian Highlands, approximately spanning the area between modern Diyabakır and Lake Van and the region west of Lake Urmia. Nairi has sometimes been equated with Nihriya, known from Mesopotamian, Hittite, and Urartian sources. However, its co-occurrence with Nihriya within a single text may argue against this.

Prior to the Bronze Age collapse, the Nairi tribes were considered a force strong enough to contend with both Assyria and Hatti. If Nairi and Nihriya are to be identified, then the region was the site of the Battle of Nihriya (c. 1230 BCE), the culminating point of the hostilities between Hittites and Assyrians for control over the remnants of the former kingdom of Mitanni.

The first kings of Urartu referred to their kingdom as Nairi instead of the native self-appellation Bianili. However, the exact relationship between Urartu and Nairi is unclear. Some scholars believe that Urartu was a part of Nairi until the former's consolidation as an independent kingdom, while others have suggested that Urartu and Nairi were separate polities. The Assyrians seem have continued to refer to Nairi as a distinct entity for decades after the establishment of Urartu, until Nairi was totally absorbed by Assyria and Urartu in the 8th century BCE.