Hipparchus was the most important astronomer of the ancient Greek world. This volume provides a comprehensive introduction to almost everything that can be known or reasonably surmised about his life and work. Hipparchus was the first to apply an effective geometric model to the cosmos, which enabled him to predict the positions of the Sun, Moon and stars more reliably than before. He was also the first to catalogue most of the stars that were visible in the northern hemisphere, giving a detailed account of their risings, settings and culminations. His most important discovery was the long-term movement of the sky, known as precession. Crucially, this study provides a translation and analysis of Hipparchus' only surviving work, the Commentary on the Phenomena of Aratus and Eudoxus, and reconstructs his catalogue of the stars, which has not survived, using a modern precession model.