The Geometry of the Three First Books of Euclid is a mathematical treatise written by the ancient Greek mathematician, Euclid. This book presents a comprehensive study of the principles of geometry and provides direct proofs of the theorems and propositions contained in the first three books of Euclid’s Elements. The author has relied solely on the definitions of the concepts and principles of geometry to derive the proofs, without making use of any additional assumptions or postulates. The book includes an introduction that discusses the fundamental principles of the science of geometry, providing readers with a solid foundation for understanding the proofs presented in the subsequent chapters. This work is an essential resource for students and scholars of mathematics, as well as anyone interested in the history of geometry and its development over time.This scarce antiquarian book is a facsimile reprint of the old original and may contain some imperfections such as library marks and notations. Because we believe this work is culturally important, we have made it available as part of our commitment for protecting, preserving, and promoting the world’s literature in affordable, high quality, modern editions, that are true to their original work.