The protagonist of the Crito (and most of Plato's dialogues). Socrates is one of the most important figures in the history of Western philosophy, standing at the origin of the rational tradition initiated by himself, Plato, and Aristotle. Socrates himself arguably never advanced any doctrines of his own. His method consisted more of questioning others who claimed to have great knowledge or wisdom, and through the elenchus, or cross- examination, showing them that they were in fact ignorant. Thus, his influence lies not in a set of theories he advanced, but his method of approaching questions, and his unrelenting scrutiny. The Crito finds him an old man of seventy, sitting in prison and awaiting execution.
An old friend of Socrates, about his age. Like many of Plato's dialogues, the Crito takes its name from Socrates' primary interlocutor. Crito is a long-time follower of Socrates, and is deeply distraught at the prospect of Socrates' impending execution. Crito, and some of Socrates' other friends, have pooled together their resources to arrange an escape for their friend and mentor. Crito is willing to make almost any sacrifice to save Socrates' life.
Not a character in the normal sense of the word; the fact that Socrates personifies the Laws of Athens in his argument is crucial to the dialogue. The Laws were originally set down by the legendary lawgiver, Solon, though they had been frequently modified since, especially during the political turmoil in Athens at the end of the 5th century B.C. The Laws are given a voice in the Crito because, for the Greeks, just or unjust action is something that one does to someone else. Socrates wants to say that escaping from prison would be unjust, but he must also say whom he would be wronging. His best answer is that he would be wronging the Laws of Athens, but in order to do so, he must treat these Laws as a human being with a human voice. Thus, Plato is not simply employing a rhetorical device in giving the Laws a voice, he is also substantiating the argument.