Arethas () is the Greek form of the Arab name al-Harith (). It can refer to:
Arethas (martyr) (died 523), Arab Christian martyr in Yemen Al-Harith ibn Jabalah, Ghassanid king (r. 528–569) Arethas of Caesarea (fl. 10th-century), Byzantine scholar and archbishop of Caesarea (modern Kayseri, Turkey)
See also Aretas (disambiguation)