Aroer (Hebrew: ערוער, עֲרֹעֵר) is a Biblical town on the north bank of the River Arnon to the east of the Dead Sea, in present-day Jordan. The town was an ancient Moabite settlement, and is mentioned in the Bible.
Henry Baker Tristram suggested that "Aroer, which is on the edge of the valley of Arnon", is the place of modern 'Ara'ir on the north bank of the Arnon ravine, about 11 miles (18 km) from the mouth of the river. The city was still standing in the time of Eusebius. This place was usually described by its situation, in order to distinguish it from other localities of the same name.
It appears first as having been captured from Moab by the Amorite king Sihon. After the Israelite attack on the Amorites, it was assigned as part of the territory of the tribe of Reuben, whose southern frontier it marked. This is the city mentioned in Numbers 32:34, with the southern towns, as having been built by the Tribe of Gad before the Tribal allotments of Israel. When Hazael of Aram Damascus took the Transjordan territory from the Kingdom of Israel, Aroer is given as its southern limit. It is clear, from Jeremiah 48:19, that the Moabites ultimately recovered it from Israel.