Mesopotamia was a region in southwestern Asia on Earth. The ancient city of Uruk, referenced in the stories of Gilgamesh and his companion Enkidu, was located here. (TNG: "Darmok")
Flint claimed to have been born as Akharin in Mesopotamia in 3834 BC. (TOS: "Requiem for Methuselah")
Mesopotamia hosted the city of Babylon, the apparent namesake of the Babel planetoid and location of the mythical Tower of Babel.