The Deuteronomist, or simply D, is one of the sources underlying the Hebrew bible (the Old Testament), together with the Priestly source and the Yahwist. It is found in the book of Deuteronomy, in the books of Joshua, Judges, Samuel, and Kings (the Deuteronomistic history, or DtrH) and also in the book of Jeremiah. (The adjectives Deuteronomic and Deuteronomistic are essentially interchangeable: if they are distinguished at all, then the first refers to Deuteronomy and the second to the history).

The Deuteronomists are seen more as a school or movement than a single author. It is generally agreed that the DtrH originated independently of both the books of Genesis, Exodus, Leviticus and Numbers (the first four books of the Torah) and the history of the books of Chronicles; most scholars trace all or most of it to the Babylonian exile (6th century BCE), and associate it with editorial reworking of both the Tetrateuch and Jeremiah.

Since the mid-20th century scholars have identified the Deuteronomists as country Levites (a junior order of priests), or as prophets in the tradition of the northern kingdom of Israel, or as sages and scribes at the royal court. Recent scholarship has interpreted the book as involving all these groups, and a broad consensus has emerged that describes the origin and growth of Deuteronomism in the following terms.