Irtysh River, Kazakh Ertis, Chinese (Pinyin) Ertix He or (Wade-Giles romanization) O-erh-ch'i-ssu Ho, real waterway of west-focal and western Asia. With a length of 2,640 miles (4,248 km), it is one of the landmass' longest waterways. The Irtysh and the Ob River, of which the Irtysh is the primary tributary, together constitute the world's seventh longest waterway framework.