D is one of the five authors (J, E, D, P, and R) of the Pentateuch or Torah (the first five books of the Bible) theorized by Biblical scholars. S/he may have lived during the 7th century BC.

D is short for the "Deuteronomist" and is credited with large parts of, as you may have guessed, Deuteronomy. D may have also had a hand in Joshua, Judges, Ruth, Samuel, and Kings, all historical scripture detailing the conquest of Canaan and the establishment of Israel. D's work includes a massive revision of religious law.

One author, Richard Elliot Friedman, suggests that the Deuteronomist may have been the prophet Jeremiah. A widely-held school of thought holds that D was Jeremiah's scribe Baruch.