Final answer:
Abraham is the man who left the Euphrates city of Ur to found a new nation, according to Genesis 15. He originated from Mesopotamia and his journey to establish a new community under God's promise is a central narrative in the Abrahamic religions.
Step-by-step explanation:
The man who left the Euphrates city of Ur to found a new nation in Genesis 15 is Abraham. According to the Hebrew Bible, Abraham originally came from Mesopotamia and is regarded as the first patriarch of the Hebrews. He and his followers migrated from Ur around 1900 BCE, making their way to Canaan under a divine promise, known as the Covenant. Despite the importance of Abraham in biblical traditions, there is little archaeological evidence to confirm his historical existence outside of the religious texts. However, the story of Abraham has been passed down through centuries and is central to the Jewish, Christian, and Islamic faiths.