Pachacuti was the ninth Sapa Inca (emperor) of the Inca Empire, reigning from 1438 to 1471. He is best known for transforming the Inca state from a small kingdom into a vast empire through extensive conquests and effective administrative reforms. His reign marked significant advancements in infrastructure, governance, and the integration of diverse cultures within the empire, laying the foundation for what would become one of the largest empires in pre-Columbian America.