He was of Gaulish ancestry, born in Arelate (Arles). He is described as a hermaphrodite (ανδροθηλυς) by birth. He received an exquisite education, first in Gallia Narbonensis and then in Rome, and at an early age began his lifelong travels through Greece, Italy and the East. His extensive knowledge, combined with great oratorical powers, raised him to eminence both in Athens and in Rome. With Plutarch, with Herodes Atticus, to whom he bequeathed his library at Rome, with Demetrius the Cynic, Cornelius Fronto, Aulus Gellius, and with Hadrian himself, he lived on intimate terms; his great rival, whom he violently attacked in his later years, was Polemon of Smyrna.
It was Favorinus who, on being silenced by Hadrian in an argument in which the sophist might easily have refuted his adversary, subsequently explained that it was foolish to criticize the logic of the master of thirty legions. When the servile Athenians, feigning to share the emperor's displeasure with the sophist, pulled down a statue which they had erected to him, Favorinus remarked that if only Socrates also had had a statue at Athens, he might have been spared the hemlock.
Hadrian banished Favorinus at some point in the 130s, to the island of Chios. Rehabilitated with the ascension of Antoninus Pius in 138, Favorinus returned to Rome, where he resumed his activities as an author and teacher of upper class pupils. His year of death is unknown, but it appears that he reached a remarkable age for his time, dying around 160 in his eighties.
Of the very numerous works of Favorinus, we possess only a few fragments, preserved by Aulus Gellius, Diogenes Laertius, Philostratus, and in the Suda, Laropia (miscellaneous history) and his memoirs. As a philosopher, Favorinus belonged to the sceptical school; his most important work in this connection appears to have been the Pyrrhonean Tropes in ten books, in which he endeavours to show that the methods of Pyrrho were useful to those who intended to practise in the law courts.