Son of the preceding, was a child at his accession, and reigned B. C. 220-163, about 57 years. (Diod. l.c. ; Just. 29.1
; Plb. 4.2
He married Antiochis, the daughter of Antiochus III., king of Syria, and, in consequence of this alliance, assisted Antiochus in his war against the Romans.
After the defeat of Antiochus by the Romans, B. C. 190, Ariarathes sued for peace in 188, which he obtained on favourable terms, as his daughter was about that time betrothed to Eumenes, the ally of the Romans. In B. C. 183-179, he assisted Eumenes in his war against Pharnaces. Polybius mentions that a Roman embassy was sent to Ariarathes after the death of Antiochus IV., who died B. C. 164. Antiochis, the wife of Ariarathes, at first bore him no children, and accordingly introduced two supposititious ones, who were called Ariarathes and Holophernes. Subsequently, however, she bore her husband two daughters and a son, Mithridates, afterwards Ariarathes V., and then informed Ariarathes of the deceit she had practised upon him.
The other two were in consequence sent away from Cappadocia, one to Rome, the other to Ionia. (Liv. 37.31
; Plb. 22.24
; Appian, App. Syr. 5
; Diod. l.c.