The Karatag or Qoratagʻ (Russian: Каратаг) is a river of northwestern Tajikistan and eastern Uzbekistan. It flows through and flows down the south slopes of the Gissar mountain range. At its confluence with the , the Surxondaryo is formed. The river is 112 kilometres (70 mi) long. Large seismic landslides occur in the river basin and it also contains several glacial lakes. Upstream from the confluence with the , the Karatag is called Diakhandara. Another tributary is the Zambar. The Diakhandara Glacier, which fed the upper course of the Karatag, has fully melted.