Sumerian is a language isolate.^{[2][12][13][14]} Ever since decipherment, it has been the subject of much effort to relate it to a wide variety of languages. Because it has a peculiar prestige as the most ancient written language, proposals for linguistic affinity sometimes have a nationalistic background. Such proposals enjoy virtually no support amongst linguists because of their unverifiability.^[15] Sumerian was at one time widely held to be an Indo-European language, but that view later came to be almost universally rejected.^[16]

A few examples of proposed linguistic affiliations include:

• Kartvelian languages^[17][18] (Nicholas Marr)
• Munda languages (Igor M. Diakonoff^[19])
• Dravidian languages (see Elamo-Dravidian^[20])
• Uralic languages (Simo Parpola^[21]) or, more generally, Ural–Altaic languages (Simo Parpola,^[21] C. G. Gostony,^[22] András Zakar,^[23] Ida Bobula^[20][24])
• Basque language (Aleksi Sahala^[20])
• Nostratic languages (Allan Bomhard^[20][25])
• Sino-Tibetan languages (Jan Braun,^[26] following C. J. Ball, V. Christian, and K. Bouda^[27]), close to Tibetan and Burmese,^[26] or, more generally, Dené–Caucasian languages (John Bengtson^[28])