"To express oneself badly is not only faulty as far as the language goes, but does some harm to the soul."—Socrates (attributed)
Socrates, commonly considered the father of philosophy, was an Athenian philosopher who lived from 469-399 BCE, when he was executed in the wake of the Peloponnesian War (of which, interestingly, he was a veteran, having served with distinction at Delium in an earlier phase of the war). Despite his reputation, he was not, by any stretch, the first philosopher -- earlier philosophers certainly existed and are, in fact, known as the "pre-Socratic philosophers".
He disapproved of writing, and so is known chiefly through the writings of his student Plato. (Another of his students, Xenophon, also wrote about him, but his works are less known.) Socrates taught and inspired many prominent young Athenians, from the aforementioned Plato to Alcibiades. (Plato even devoted a good chunk of his Symposium to defending against the common charge that Socrates had an affair with Alcibiades).