Ishim River (; ) is a river running through Kazakhstan and Russia. It is long; its average discharge is . It is a left tributary of the Irtysh River. The Ishim River is partly navigable in its lower reaches. The upper course of the Ishim passes through Astana, the capital of Kazakhstan. In Russia, the river travels through a vast marshland for its course, and has countless meanders and oxbow lakes. The river freezes from late November until March.