Deuteronomy (Ancient Greek: Δευτερονόμιον, romanized: Deuteronómion, lit. 'second law') is the fifth book of the Torah (in Judaism), where it is called Devarim (Hebrew: דְּבָרִים‎, Dəḇārīm, '[the] words [of Moses]') and the fifth book of the Christian Old Testament.

Chapters 1–30 of the book consist of three sermons or speeches delivered to the Israelites by Moses on the Plains of Moab, shortly before they enter the Promised Land. The first sermon recounts the forty years of wilderness wanderings which had led to that moment and ended with an exhortation to observe the law. The second sermon reminds the Israelites of the need to follow Yahweh and the laws (or teachings) he has given them, on which their possession of the land depends. The third sermon offers the comfort that, even should the nation of Israel prove unfaithful and so lose the land, with repentance all can be restored.

The final four chapters (31–34) contain the Song of Moses, the Blessing of Moses, and the narratives recounting the passing of the mantle of leadership from Moses to Joshua and, finally, the death of Moses on Mount Nebo.

One of its most significant verses is Deuteronomy 6:4, the Shema Yisrael, which has been described as the definitive statement of Jewish identity for theistic Jews: "Hear, O Israel: the LORD our God, the LORD is one." Verses 6:4–5 were also quoted by Jesus in Mark 12:28–34 as the Great Commandment.