The main river that flows through Baghdad is the Tigris River. This river is historically significant, serving as a critical waterway for ancient civilizations, including the Mesopotamians. The Tigris, along with the Euphrates River, forms one of the cradles of civilization, often referred to as the Fertile Crescent. Today, it remains vital for agriculture, transportation, and water supply in the region, shaping the landscape and history of modern-day Iraq.