Tannu Uriankhai (Tuvan: Таңды Урянхай, [taŋˈdɤ urʲanˈχaj]; Mongolian: Тагна Урианхай, romanized: Tagna Urianhai, [ˈtʰaɢəɴ ʊrʲæŋˈχæɪ̯]; simplified Chinese: 唐努乌梁海; traditional Chinese: 唐努烏梁海; pinyin: Tángnǔ Wūliánghǎi) was a historical region of the Mongol Empire, its principal successor, the Yuan dynasty, and later the Qing dynasty. The territory of Tannu Uriankhai largely corresponds to the modern-day Tuva Republic of the Russian Federation, neighboring areas in Russia, and a small part of the modern state of Mongolia.
Tannu designates the Tannu-ola Mountains in the region, and Uriankhai was the Mongolian name for the Tuvans (and accordingly their realm), which meant "the people living in the woods" (Chinese: 林中百姓; pinyin: Línzhōng Bǎixìng).