What river serves as the longer of the two rivers that define Mesopotamia?

The Euphrates River is the longer of the two rivers that define Mesopotamia, which is an ancient region located between the Tigris and Euphrates Rivers, primarily in modern-day Iraq, but also extending into parts of Syria and Turkey. The Euphrates runs for about 2,800 kilometers (1,700 miles), making it one of the longest rivers in Western Asia.

Mesopotamia is often referred to as the "cradle of civilization" due to its role in early human history, and the Euphrates, together with the Tigris, has provided the necessary water resources for agriculture, trade, and societal development in this region. The interplay between these two rivers has been crucial for the establishment of some of the world's earliest cities and cultures in ancient times.

While the Tigris is also significant and serves as a vital water source for the region, it is shorter than the Euphrates, which solidifies the latter's status as the defining river of Mesopotamia that contributed immensely to its agricultural and cultural wealth.