Abraham is the point at which Judaism, Christianity and Islam meet, and there is no evidence for him outside their scriptures.
The Genesis narrative gives him a migration from Ur of the Chaldeans through Haran to Canaan, a covenant sealed by circumcision, a promise of descendants as numerous as the stars, the birth of Ishmael to Hagar and Isaac to Sarah, and the near-sacrifice of a son. He is placed by the internal chronology of the Hebrew Bible in roughly the early second millennium BCE.
No inscription, archive or archaeological layer names him. This is not surprising for a pastoralist rather than a king, but it means the case rests entirely on whether the narrative preserves early memory. Mid twentieth-century archaeologists, led by William F. Albright, argued that the customs described, adoption practices, treaty forms, personal names, fit a second-millennium background and vindicated the patriarchal narratives. That case was dismantled from the 1970s by Thomas L. Thompson and John Van Seters, who showed the parallels fitted the first millennium at least as well, and pointed to anachronisms in the text: domesticated camels used as pack animals, Philistines in Gerar, and Ur described as Chaldean, a designation that belongs to the first millennium.
The current spread of scholarly opinion runs from a substantially later composition of the narratives in the exilic or post-exilic period, with no recoverable historical figure behind them, to the view that older traditions were reworked. Almost no one now defends the Albright synthesis. Nothing in this settles what the figure means to the traditions that trace themselves to him.