(Sept. Ἀγαθοῦ, Ἀγαθοῦ, and Πατᾶ; Vulg. Haiz) a royal city of the Canaanites, east of Bethel. It existed in the time of Abraham, who pitched his tent between the two cities (Gen. xii. 8; xiii. 3); but it is chiefly noted for its capture and destruction by Joshua (vii. 2-5; viii. 1-29). At a later period Ai was rebuilt, and is mentioned by Isaiah (x. 28), and also after the captivity. The site was known, and some scanty ruins still existed, in the time of Eusebius and Jerome (Onomast. in Agai), but Dr Robinson was unable to discover any certain traces of either. He remarks (Bib. Researches, ii. 313), however, that its situation with regard to Bethel may be well determined by the facts recorded in Scripture: That Ai lay to the east of Bethel is distinctly stated; and the two cities were not so far distant from each other but that the men of Bethel mingled in the pursuit of the Israelites as they feigned to flee before the king of Ai, and thus both cities were left defenceless (Josh. viii. 17). A little to the south of a village called Deir Diwan, and one hour's journey from Bethel, the site of an ancient place is indicated by reservoirs hewn in the rock, excavated tombs, and foundations of hewn stone. This, Dr Robinson inclines to think, may mark the site of Ai, as it agrees with all the intimations as to its position.