Umar, also known as Umar ibn al-Khattab, was the second caliph of the Rashidun Caliphate and ruled from 634 to 644 CE. He is known for his strong leadership and administrative skills, which helped expand the Islamic empire significantly during his reign. Umar played a crucial role in the early spread of Islam and is remembered for his just governance and reforms. Umar was born in 584 CE in Mecca and initially opposed the teachings of Prophet Muhammad. However, he converted to Islam in 616 CE and became one of the Prophet's closest companions. His contributions to Islamic law and society are still influential today, and he is often regarded as one of the greatest caliphs in Islamic history.