Kathu (Thou; Chinese: 嘎苏话) is a Lolo-Burmese language of Balong (坝聋), Nanping Township (南屏镇), Guangnan County, Yunnan, China. 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), as well as in Jinping County, Yunnan.
Kathu 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). Wu (2004) lists the onset clusters pl, pʰl, bl, ml, kl, kʰl, gl, ql, qʰl, ɢl, ŋl.
Hsiu (2014:65) identifies two varieties, both spoken in Nanping Township (南屏镇).
- Kathu (autonym: ka˧θu˧), spoken in Anwang village 安王村
- Thou (autonym: θou̯˥˧), spoken in Balong village 坝聋村
- Kathu at Ethnologue (18th ed., 2015)
- Hammarström, Harald; Forkel, Robert; Haspelmath, Martin; Bank, Sebastian, eds. (2016). "Kathu". Glottolog 2.7. Jena: Max Planck Institute for the Science of Human History.
- Hsiu, Andrew. 2014. "Mondzish: a new subgroup of Lolo-Burmese". In Proceedings of the 14th International Symposium on Chinese Languages and Linguistics (IsCLL-14). Taipei: Academia Sinica.
- Wu Zili [武自立]. 1994. A preliminary study of the Gasu language of Guangnan County, Yunnan Province [云南省广南县嘎苏话初探]. Minzu Yuwen 2. http://wuxizazhi.cnki.net/Search/MZYW402.006.html
- Wu Zili [武自立]. 2004. "Gasu language [嘎僳话]". In Studies on selected languages of Yunnan [云南特殊语言研究], 486-513. Kunming: Yunnan People's Press [云南民族出版社]. ISBN 7536730624