Omsk (; Russian: Омск, IPA: [omsk]) is the administrative center and largest city of Omsk Oblast, Russia. It is situated in southwestern Siberia, and has a population of over 1 million. Omsk is the second-largest city in Siberia after Novosibirsk, and is ninth-largest city in Russia. It is an essential transport node, serving as a train station for the Trans-Siberian Railway and as a staging post for the Irtysh River.