The Tannu-Ola mountains (Tuvan: Таңды-Уула, Tañdı-Uula, Uniform Turkic Alphabet: [Taᶇdь-Uula] Error: {{Lang}}: Non-latn text (pos 5: ь)/Latn script subtag mismatch (help), Tuvan pronunciation: [tʰaŋˈtɯ ˈuːla] – Tangdy-Uula mountains; Mongolian: Тагнын нуруу, Tağnîn nurú, Mongolian pronunciation: [tʰaɢˈniŋ nʊˈrʊː], Russian: Танну-Ола, [tɐnˈnu ɐˈla]) is a mountain range in southern Siberia, in the Tuva Republic of Russia.

The northern slopes are part of the watershed of the Yenisei River, facing the western Sayan Mountains.

The eastern end touches the large watershed of the Selenge River in Mongolia.

They form the northern limits of a large basin of steppes that extends south to the Mongolian Altay Mountains and includes the salt lake Uvs Nuur.

The western end is located near the northern Altay Mountains in the Russian Altai Republic.