Mesopotamia is a historical region of West Asia situated within the Tigris–Euphrates river system, in the northern part of the Fertile Crescent. Today, Mesopotamia is known as present-day Iraq and forms the eastern geographic boundary of the modern Middle East. Just beyond it lies southwestern Iran, where the region transitions into the Persian plateau, marking the shift from the Arab world to Iran. In the broader sense, the historical region of Mesopotamia also includes parts of present-day Iran (southwest), Turkey (southeast), Syria (northeast), and Kuwait.