|Covid-19|Danish Vikings land in the Breton March (western part of Gaul). Duke Nominoe of Brittany fails to withstand them in battle, but succeeds in buying them off with gifts and persuading the Vikings to leave (approximate date).
The Saracens, under the Berber leader Kalfun, capture the Byzantine city of Bari (Southern Italy). He becomes the first ruler of the Emirate of Bari, and expands his influence on the Italian mainland with raids.
August 10 – Caliph Al-Wathiq dies of dropsy after a five-year reign. He is succeeded by his brother al-Mutawakkil.
January 24 – Pope Sergius II dies of gout after a 3-year reign. He is succeeded by Leo IV, as the 103rd pope of Rome.
April 21– Rabanus Maurus, a Frankish Benedictine monk, becomes archbishop of Mainz after the death of Odgar.
Æthelred I, king of Wessex (approximate date)
Al-Mu'tazz, Muslim caliph (d. 869)
Charles the Child, king of Aquitaine (or 848)
Cheng Ji, Chinese general (approximate date)
Fujiwara no Sukeyo, Japanese aristocrat (d. 897)
Kang Junli, general of the Tang Dynasty (d. 894)
Lu Yi, chancellor of the Tang Dynasty (d. 905)
Miyoshi Kiyotsura, Japanese scholar (d. 918)
Wang Jian, emperor of Former Shu (d. 918)
Wang Jingchong, Chinese general (d. 883)
January 24 – Sergius II, pope of the Catholic Church
April 21 – Odgar, Frankish monk and archbishop
June 1 – Xiao, empress of the Tang Dynasty
June 14 – Methodius I, patriarch of Constantinople
August 10 – Al-Wathiq, Muslim caliph (b. 816)
Fedelmid mac Crimthainn, king of Munster (Ireland)
Frothar of Toul, Frankish bishop (approximate date)
Hetto, Frankish archbishop (approximate date)
Isa ibn Mansur al-Rafi'i, Muslim governor
Muhammad ibn al-Zayyat, Abbasid vizier
Li Rangyi, chancellor of the Tang Dynasty
Theodemar of Iria, Galician bishop
Year 847 (DCCCXLVII) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar.