The Altai Mountains (/ɑːlˈtaɪ/), also spelled Altay Mountains, are a mountain range in Central and East Asia, where Russia, China and Mongolia converge, and where the rivers Ob and Irtysh have their headwaters. The massif merges with the Sayan Mountains in the northeast, and gradually becomes lower in the southeast, where it merges into the high plateau of the Gobi Desert.