Beth Nahrain or Bet Nahrain or (Syriac: ܒܝܬ ܢܗܪ̈ܝܢ, translit. Bêṯ Nahrayn; "between (two) rivers," often erroneously translated as "house of the (two) rivers") is name for the region known as Mesopotamia in the Syriac language. Geographically, it refers to the areas between and surrounding the Euphrates and Tigris rivers (as well as their tributaries). The Aramaic name loosely describes the area of the rivers, not only literally between the rivers. The area is considered by Assyrians as their homeland.
While it may be thought that the name is derived from Mesopotamia (Ancient Greek: Μεσοποταμία), the opposite is more probable. The Aramaic name has been attested since the adoption of Old Aramaic as the lingua franca of the Neo Assyrian Empire in the 8th century BCE, but the Greek name Mesopotamia was first coined in the 2nd century BCE by the historian Polybius during the Seleucid period. The name Bayn al-Nahrayn is also found in Arabic (بين النهرين; "between the two rivers").
This area roughly encompasses almost all of present-day Iraq, parts of southeastern Turkey, and northeastern Syria. The Assyrians are considered to be indigenous inhabitants of Beth Nahrain. "Nahrainean" or "Nahrainian" is the Anglicized name for "Nahrāyā", which is the Aramaic equivalent of "Mesopotamian".