a river in Tomsk Oblast, RSFSR; flows in its upper course along the border with Novosibirsk Oblast. Right tributary of the Chaia River (Ob’ basin). Length, 430 km; basin area, 6,130 sq km. It flows along the eastern part of the Vasiugan’e. The river is fed by snow and rain; high water is from May through early August. The modulus of discharge increases sharply from its upper course to its lower course. The average water discharge is 7.3 m³/sec. The Iksa is used for floating logs in its lower course.