The Little Zab or Lower Zab is a river that originates in Iran and joins the Tigris just south of Al Zab in the Kurdistan region of Iraq. The Little Zab is approximately 400 kilometres (250 mi) long and drains an area of about 22,000 square kilometres (8,500 sq mi). The river is fed by rainfall and snowmelt, resulting in a peak discharge in the spring and low water in the summer and early fall. Two dams built on the Little Zab regulate the river flow, providing water for irrigation and generating hydroelectricity. The Zagros Mountains have been populated since at least the Lower Palaeolithic, but the earliest archaeological site in the Little Zab basin, Barda Balka, dates to the Middle Palaeolithic. Human occupation of the Little Zab basin has been attested for every period since then.

The Tigris is the eastern of the two great rivers that define Mesopotamia, the other being the Euphrates. The river flows south from the mountains of the Taurus in Turkey, then through the Syrian and Arabian Deserts, emptying into the Persian Gulf.