Ariarathes IV Eusebes (reigned in 220–163 BCE), son of the king of Cappadocia Ariarathes III and Stratonice, is a child at his accession, and reigns for about 57 years.

He marries Antiochis, the daughter of Antiochus III the Great, king of Syria, and wife Laodice III, and, in consequence of this alliance, assists Antiochus in his war against the Romans.