Kathu (Chinese: 嘎苏话) is a Lolo-Burmese language of Balong (坝聋), Nanping Township (南屏镇), Guangnan County, Yunnan, China.^[2] The Kathu are locally known as the White Yi (白彝). Wu Zili (2004) estimates that Kathu has a total of more than 7,000 speakers in Guangnan County (including in Dayashao 大牙少^[3]), as well as in Jinping County, Yunnan. Ethnologue mentions a possible presence in Guangxi Province.

A related variety is known as Thou.

Kathu-Thou is notable for having initial consonant clusters, which within the Lolo-Burmese branch are also found in Written Burmese (Old Burmese) and Jinuo (Hsiu 2014:66).^[4] Wu (2004) lists the onset clusters pl, pʰl, bl, ml, kl, kʰl, gl, ql, qʰl, ɢl, ŋl.

Hsiu (2014:65)^[4] identifies two varieties, both spoken in Nanping Township (南屏镇).

• Kathu (autonym: ka33 θu33), spoken in Anwang village 安王村
• Thou (autonym: θou̯53), spoken in Balong village 坝聋村

Kathu vocabulary is largely similar to those of other Mondzish languages. However, there are various words that do not appear to be of Lolo-Burmese origin, and are derived from an unknown Tibeto-Burman branch (Hsiu 2014).^[4] Hsiu (2014) suggests that Kathu could be added to George van Driem's list of Trans-Himalayan "fallen leaves."

Bradley (1997)^[5] classified Kathu as a Northern Loloish language, while Bradley (2007)^[6] classified it as a Southeastern Loloish language. However, Pelkey (2011:458)^[7] notes that Kathu and Mo'ang are not Southeastern Loloish languages.

• Kathu word list (Wiktionary)