Republic was written by Plato.
Plato was a Greek philosopher who lived in Athens around 428 to 348 BC. He was a student of Socrates and later became the teacher of Aristotle. Republic is his most famous work, written in the form of a dialogue where Socrates discusses justice, the ideal city-state, and the qualities of a good ruler.
The book introduces the idea of a philosopher-king, a ruler who governs through wisdom rather than force. It also contains the famous allegory of the cave, which explains how people mistake shadows for reality. Republic is still studied today as one of the foundational texts of political philosophy and ethics.