The Apology of Socrates, by Plato. Part II.

The Apology of Socrates, written by Plato, is a Socratic dialogue of the speech of legal self-defense which Socrates spoke at his trial for impiety and corruption in 399 BC. The dialogue is a defense against the charges of "corrupting the youth" and "not believing in the gods in whom the city believes, but in other Daimonia that are novel" to Athens.  

Among the primary sources about the trial and death of the philosopher Socrates (469-399 BC), The Apology of Socrates is the dialogue that depicts the trial, and it's one of four Socratic dialogues along with Euthyphro, Phaedo, and Crito, through which Plato describes the final days of the philosopher Socrates. (From Wikipedia).