Probably a son of Tiberius *Claudius Thrasyllus and shared his astrological lore. (See astrology.) He was ADC (praefectus fabrum, see fabri) to *Claudius and tribune of Legio XX in the invasion of Britain in 43 ce, winning decorations; he served as secretary dealing with Greek embassies and applications, and held posts in Egypt, including headship of the *Museum at *Alexandria (1). Favoured by *Iulia Agrippina, he was prefect of Egypt from 55 until her death in 59. He survived until the reign of *Vespasian, who allowed him honours from Ephesus; his daughter married Epiphanes of *Commagene and he was grandfather of *Iulius Antiochus Epiphanes Philopappus (suffect consul 109). Seneca Q.Nat. 4. 2. 13 describes Balbillus as exceptionally gifted in every branch of literature; fragments of his Astrologumena are preserved (CCAG 8. 3. 103, 8. 4. 233). (The identity of astrologer and prefect was denied by A.