Onguday (Russian: Онгуда́й; Altay: Оҥдой, Oñdoy) is a rural locality (a selo) and the administrative center of Ongudaysky District in the Altai Republic, Russia, located on the Ursul River, 210 kilometers (130 mi) from Gorno-Altaysk, the capital of the republic.

[citation needed] Local name Ongdoy (from mongolian onge — "cave, cavity", doy — possession affix;literally — "having cave, cavities" It was founded in 1626.

[citation needed] In 1856-1857, the camp-settlement of the Altai spiritual mission of the Russian Orthodox Church was founded.

Onguday has a monsoon-influenced humid continental climate (Köppen climate classification Dwb) with warm, humid summers and severely cold, dry winters.

[citation needed] The coldest month of the year is January, when the average temperature is −19.5 °C (−3.1 °F), with the record low of −43.9 °C (−47.0 °F).