Socrates—narrator of the book.
Glaucon—son of Ariston (and brother of Plato, who does not appear). Presents the view that justice is something the weak attempt to force on the strong.
Adeimantus—brother of Glaucon. Describes justice as accomplished for its practical benefits. He and Glaucon are the only ones who respond to Socrates’ questions after Book I.
Polemarchus—host to the gathering at which Socrates speaks. He describes justice as giving others what they deserve.
Cephalus—elderly gentleman, Polemarchus’ father. He defines justice as honesty and returning what one takes from others.
Thrasymachus—teacher of rhetoric (“sophist”). He argues the position that might makes right.
Cleitophon, Lysias, Euthydemus, Niceratus, Charmanides—other guests at Polemarchus’.