Syr Darya is one of the two major rivers (darya) of Central Asia that supports the vast irrigation networks of Fergana Valley and the northern parts of Uzbekistan and Southern Kazakhstan. The second major Central Asian river is the Amu Darya that has a more southern route but the waters of both finally reach the same destination, the Aral Sea. Syr Darya feeds the Northern Aral Sea which is separated by a dam from the larger and largely shrunken, southern part of the lake. On its way, Syr Darya irrigates the most fertile regions of Central Asia and passes cities like Kokand, Khujand, Kyzylorda and Turkestan.

The river originates from the Tian Shan mountains of Kyrgyzstan and Uzbekistan. The larger part of the water is coming from the Naryn river in Kyrgyzstan, accompanied by the waters from the Kara Darya. These two confluence in the Fergana valley, nearby Namangan. Syr Darya is also marking the northern border of the Kyzyl Kum (red sands) desert. 

In the past, Syr Darya was called the Jaxartes and the name was most likely given by Alexander the Great who fought the local tribes at the shores of the river. He also founded the furthest Alexandria near the shore of Syr Darya, a city that is nowadays called Khujand. The ruins of the citadel of Alexander are still visible in in the center of the city which is considered nowadays the “Northern Capital of Tajikistan”.