Omsk is a city and the administrative center of Omsk Oblast, Russia, located in southwestern Siberia 2,236 kilometers (1,389 mi) from Moscow. With a population of 1,154,116, it is Russia's third-largest city east of the Ural Mountains after Novosibirsk and Yekaterinburg, and seventh by size nationally. Omsk acts as an essential transport node, serving as a train station for the Trans-Siberian Railway and as a staging post for the Irtysh River.

During the Imperial era, Omsk was the seat of the Governor General of Western Siberia and, later, of the Governor General of the Steppes. For a brief period during the Russian Civil War in 1918–1920, it served as the capital of the anti-Bolshevik Russian State and held the imperial gold reserves.

Omsk serves as the episcopal see of the bishop of Omsk and Tara, as well as the administrative seat of the Imam of Siberia.