The poorly attested Kassite language may have been related to Hurrian.
Hurrian was the language of the Hurrians (occasionally called "Hurrites"), and was spoken in the northern parts of Mesopotamia and Syria and the southeastern parts of Anatolia between at least last quarter of the third millennium BC and its extinction towards the end of the second millennium BC. There have been various Hurrian-speaking states, of which the most prominent one was the kingdom of Mitanni (1450–1270 BC). It has also been proposed that two little known groups, the Nairi and the Mannae, might have been Hurrian speakers, but as little is known about them, it is hard to draw any conclusions about what languages they spoke. Furthermore, the Kassite language was possibly related to Hurro-Urartian. Francfort and Tremblay on the basis of the Akkadian textual and archaeological evidence, proposed to identify the kingdom of Marhashi and Ancient Margiana. The Marhashite personal names seems to point towards an Eastern variant of Hurrian or another language of the Hurro-Urartian language family.
There was also a strong Hurrian influence on Hittite culture in ancient times, so many Hurrian texts are preserved from Hittite political centres. The Mitanni variety is chiefly known from the so-called "Mitanni letter" from Hurrian Tushratta to pharaoh Amenhotep III surviving in the Amarna archives. The "Old Hurrian" variety is known from some early royal inscriptions and from religious and literary texts, especially from Hittite centres.