The major river that flows through **Baghdad** is the **Tigris** River. This river is one of the two great rivers of Mesopotamia, the other being the **Euphrates**. The Tigris is historically significant, as it supported ancient civilizations, including the **Sumerians**, **Babylonians**, and **Assyrians**. Today, it remains crucial for irrigation, water supply, and navigation in Iraq. The river contributes to the agriculture and economy of the surrounding areas, making it a vital resource for local populations.