Tosu (Chinese: 多续 Duōxù) is a possibly extinct Qiangic language of China which shows strong affiliations to both the Loloish languages and to Tangut (Hsi-hsia). Yu (2012) classifies it as an Ersuic language, which belongs to the Qiangic branch. According to Yu (2012:1-2), there are "almost no Tosu speakers left", or "practically" no Ersu speakers left.
- Yu, Dominic. 2012. Proto-Ersuic. Ph.D. dissertation. Berkeley: University of California, Berkeley, Department of Linguistics.
- Tatsuo Nishida, 1973, 多続訳語の研究 : 新言語トス語の構造と系統 [A Study of the Tosu–Chinese Vocabulary Tosu I-yu: the structure and lineage of Tosu, a new language], 松香堂 Shokado, Kyoto (Japanese)
- T. Nishida, 1975, "Hsi-hsia, Tosu, and Lolo–Burmese", Sino-Tibetan Conference VIII, Berkeley
- T. Nishida, 1976, "Hsi-hsia, Tosu, and Lolo–Burmese languages", Studia Phonologica 10:1–15