A Peripatetic philosopher of Mitylene, accompanied Pompey in his flight after the battle of Pharsalia, B.C. 48. He afterwards settled at Athens, where the young M. Cicero was his pupil in B.C. 44. By the elder Cicero's influence, Cratippus received the gift of Roman citizenship from Caesar.

Plutarch, Cicero:

Moreover, of the men of his own time who were famous for eloquence or learning, there is not one whom he did not make more famous by what he said or wrote in favour of him. For Cratippus the Peripatetic he obtained the Roman citizenship from Caesar, now in power, and he also induced the council of the Areopagus to pass a decree requesting him to remain at Athens and discourse with the young men, and thus be an ornament to the city. Furthermore, there are letters from Cicero to Herodes, and others to his son, in which he urges them to study philosophy with Cratippus

Parts from Harry Thurston Peck. Harpers Dictionary of Classical Antiquities. New York. Harper and Brothers. 1898.