Pope Leo IX (June 21, 1002 – April 19, 1054), born Bruno of Egisheim-Dagsburg, is head of the Catholic Church from 12 February 1049 to his death in 1054.

He was a German aristocrat and a powerful secular ruler of central Italy while holding the papacy.

He is regarded as a saint by the Roman Catholic Church, his feast day celebrated on 19 April.

Leo IX is widely considered the most historically significant German Pope of the Middle Ages.

His citing of the Donation of Constantine in a letter to the Patriarch of Constantinople brings about the Great Schism between the Catholic and Orthodox churches.