Umar I, also known as Umar ibn al-Khattab, was the second caliph of the Rashidun Caliphate, ruling from 634 to 644 CE. He is known for his significant contributions to the expansion of the Islamic empire, overseeing conquests in Persia, Syria, and Egypt. His leadership style emphasized justice and consultation, earning him respect among his followers. Umar I is also recognized for implementing administrative reforms and establishing a legal framework that included the Islamic calendar. He was a close companion of the Prophet Muhammad and played a crucial role in the early development of the Islamic community. His assassination in 644 marked a pivotal moment in Islamic history.