The Arnon (אַרְנוֹן) is a major wadi flowing west into the Dead Sea, today known as Wadi al-Mujib in Jordan. It served as the northern boundary of Moab and the southern boundary of the Amorite kingdom of Sihon. The river appears frequently in the Pentateuch and historical books as a key geographical and covenant landmark in Israel's conquest narrative.
The Arnon's theological significance is tied to the theme of divine inheritance and boundary. When Israel crossed the Arnon, they were no longer wandering but conquering — God had delivered Sihon into their hand north of the river (Numbers 21:21–30; Deuteronomy 2:24–37). The later tribal allotments set the Arnon as the boundary for Reuben and Gad (Joshua 13), demonstrating God's precise sovereignty over the land. Isaiah 16:2 and Jeremiah 48:20 reference Moab at the Arnon in prophecy.