There is no definitive answer, but scholars tend toward modern-day Iraq as the location. Genesis 2:10-14 tells provides some clues:
A river flowed out of Eden to water the garden, and there it divided and became four rivers. The name of the first is Pishon; it is the one which flows around the whole land of Havilah, where there is gold; and the gold of that land is good; bdellium and onyx stone are there. The name of the second river is Gihon; it is the one which flows around the whole land of Cush. And the name of the third river is Tigris, which flows east of Assyria. And the fourth river is the Euphrates.
Because “the land of Cush” is associated with a region in central Africa, that region has been proposed by some scholars.
However, ancient Mesopotamia was located between two rivers, the Tigris and Euphrates. In addition, Mesopotamia is a Greek word meaning “the land between the rivers.” Ancient Mesopotamia corresponds to modern-day Iraq and parts of neighboring countries.