Umar, also spelled Omar (Umar ibn Al-Khattab, born 579 CE – died 6 November 644 CE), is one of the most powerful and influential Muslim caliphs (rulers) in history.

He is a sahābi (companion) of the Islamic prophet Muhammad.

He succeeded Caliph Abu Bakr (632–634) as the second Caliph of Rashidun Caliphate on August 23, 634.

He is an expert Islamic jurist and is best known for his pious and just nature, which earns him the title Al-Faruq ("the one who distinguishes between right and wrong").

He is sometimes referred to as Caliph 'Umar I by historians of Islam, since a later Umayyad caliph, 'Umar II, also bears that name.

Under Umar the Islamic empire expands at an unprecedented rate ruling the whole Sassanid Persian Empire and more than two thirds of the Eastern Roman Empire.

His attacks against the Sassanid Persian Empire result in the conquest of the Persian empire in less than two years.

It is Umar, according to Jewish tradition, who sets aside the Christian ban on Jews and allows Jews into Jerusalem and to worship.