Prodicus of Ceos (c. 465 - 415) was a Greek philosopher, part of the first generation of Sophists. "He was a Sophist in the full sense of a professional freelance educator."

He came to Athens as ambassador from Ceos, and became known as a speaker and a teacher. Like Protagoras, he professed to train his pupils for domestic and civic service; but it would appear that, while Protagoras's chief instruments of education were rhetoric and style, Prodicus made linguistics prominent in his curriculum.

Several of Plato's dialogues focus upon Prodicus' linguistic theory, and his insistence upon the correct use of names. There seems to have been a standing joke about the difference between his one-drachma and fifty-drachma lecture.

In the Cratylus (384b) Socrates says that if he could have afforded the fifty drachmas he would now be an expert on "the correctness of names." In several of the Platonic dialogues Socrates appears as the friend and companion of Prodicus, which reveals at least that the two did have close personal relations, and that Socrates did attend at least a few of his lectures. "For Socrates, correct language was the prerequisite for correct living (including an efficient government).

But Prodicus, though his linguistic teaching undoubtedly included semantic distinctions between ethical terms, had stopped at the threshold. The complete art of logoi embraced nothing less than the whole of philosophy."

While the essence of his teaching seems to have been linguistic, the Suda identifies Prodicus rather as "a natural philosopher and Sophist." In addition, Galen, includes him in a list of writers on nature. Galen also writes that he brought the linguistic discipline to bear on physiological terms. If Prodicus did contribute to natural philosophy there are no extant texts or testimonia that would illuminate his contributions.

Much of the content, if not the actual words, of one of his rhetorical displays are known today. The speech was apparently a fable detailing the education of Heracles by Virtue. The text of the fable is to be found in the "Memorabilia" of Xenophon.

Prodicus' outlook, like those of his fellow Sophists, was humanistic, and he interpreted religion through the framework of naturalism. "His theory was that primitive man was so impressed with the gifts nature provided him for the furtherance of his life that he believed them to be the discovery of gods or themselves to embody the godhead. This theory was not only remarkable for its rationalism but for its discernment of a close connection between religion and agriculture." Prodicus