The Tigris is a river in the Middle East. It is one of two rivers that define Mesopotamia. Mesopotamia literally means (the land) between the rivers. The other river is called Euphrates. The source of the river is in the Taurus mountains in Turkey. From there, it flows through various countries, most notably Turkey, Syria and Iraq. The river is 1,900 kilometres long. It comes together with the Euphrates in the Shatt-al-Arab(which is called Arvand Rud in Persian). The Shatt-al-Arab flows into the Persian Gulf.