The Tigris–Euphrates river system is a large river system in Western Asia which discharges into the Persian Gulf. Its principal rivers are the Tigris and Euphrates along with smaller tributaries.

From their sources and upper courses in the mountains of eastern Turkey, the rivers descend through valleys and gorges to the uplands of Syria and northern Iraq and then to the alluvial plain of central Iraq. Other tributaries join the Tigris from sources in the Zagros Mountains to the east. The rivers flow in a south-easterly direction through the central plain and combine at Al-Qurnah to form the Shatt al-Arab and discharge into the Persian Gulf. The rivers and their tributaries drain an area of 879,790 km², including almost the entire area of Iraq as well as portions of Turkey, Syria, Iran, and Kuwait.

The region has historical importance as part of the Fertile Crescent region, in which Mesopotamian civilization first emerged.