(Θεαίτητος), a Rhodian, who was one of the leaders of the party in his native city favourable to the Roman cause. He is first mentioned as accompanying Philophron on an embassy to the ten Roman deputies, who after the defeat of Antiochus settled the affairs of Asia, B. C. 189. (Plb. 23.3.) During the war between the Romans and Perseus, his name is again repeatedly associated with that of Philophron : their efforts to oppose all concessions to the Macedonian king and his partisans, have been already related. [PHILOPHRON.] Hence when the defeat of Perseus gave the decided preponderance to the Roman party, the Rhodians hastened to appoint Theaetetus their admiral, an office of the highest rank in that naval republic, and at the same time sent him as their ambassador to Rome, to intercede in favour of his native city. But the advanced age of their deputy frustrated their intentions : Theaetetus, who was above 80 years old, dying at Rome before the senate had come to a decision concerning his countrymen. (Plb. 27.11, 28.2, 14, 29.5, 30.5, 19.)