2. The Tigris River: The Tigris River is one of the two main rivers that define the ancient region of Mesopotamia (the other being the Euphrates). It originates in eastern Turkey and flows through Iraq before merging with the Euphrates to form the Shatt al-Arab, which empties into the Persian Gulf.
3. The Euphrates River: The Euphrates River is the other main river of Mesopotamia. It also originates in eastern Turkey and flows through Syria and Iraq before joining the Tigris River. The Euphrates is an important source of water for irrigation and has supported agricultural civilizations for thousands of years.