Which Old Testament prophet said "Thou art the man"?

The Old Testament prophet who said “Thou art the man” was Nathan. He confronted King David after David arranged the death of Uriah so he could take Uriah’s wife, Bathsheba.

Nathan first told David a parable about a rich man who stole a poor man’s beloved lamb. David angrily condemned the rich man, and Nathan revealed that the story represented David’s own actions. The phrase “Thou art the man” made the accusation personal and unmistakable.

Nathan was a court prophet and adviser during David’s reign. His rebuke led David to acknowledge his sin, although the biblical account also describes serious consequences for David’s household. A common mix-up is to attribute the phrase to Samuel, another prophet associated with Israel’s kings; Samuel rebuked Saul, but Nathan delivered this specific line to David.