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Events

April 21 – Bardas, the regent of the Byzantine Empire, is murdered by Basil the Macedonian at Miletus, while conducting a large-scale expedition against the Saracen stronghold of Crete.

May 26 – Basil the Macedonian is crowned co-emperor of the Byzantine Empire, and is adopted by the much younger Michael III.

May 27 – King Ordoño I, ruler of the Kingdom of Asturias, dies after a 16-year reign. He is succeeded by his son, Alfonso III, who later is referred to as "Alfonso the Great".
July 2 – Battle of Brissarthe: Frankish forces, led by Robert the Strong, are defeated by a joint Breton-Viking army.
Louis II, Holy Roman Emperor, defeats the Saracen invaders who are ravaging southern Italy.

The Great Heathen Army of the Vikings rides north to Northumbria. The Northumbrians are preoccupied with a civil war, and the Danes enter York unopposed.<ref>John Haywood (1995). Historical Atlas of the Vikings, p. 62. Penguin Books: Template:ISBN</ref>

An army in Lucera is assembled by orders of Louis II in preparation for an attack on the Emirate of Bari.<ref>Template:Cite book</ref>

October 17 – Caliph al-Musta'in is put to death, after a 4-year reign. He is succeeded by al-Mu'tazz, who becomes the youngest Abbasid caliph to assume power.<ref>History of the Arabs by Philip K. Hitti.</ref>
The Kharijite revolt against the Abbasid Caliphate begins in Al-Jazira (Upper Mesopotamia), which will last for 30 years.

Fujiwara no Yoshifusa becomes regent (sesshō) to assist the child emperor Seiwa, starting the Fujiwara regency.

Boris I, ruler (knyaz) of the Bulgarian Empire, sends a diplomatic mission, led by the Bulgarian nobleman Peter, to Rome, in an effort to renew ties with the West.
Pope Nicholas I orders that all Catholics should abstain from eating the "flesh, blood, or marrow"<ref>Template:Cite news</ref> of warm-blooded animals on Wednesdays and Fridays.<ref>Template:Cite web</ref>
Pope Nicholas I forbids the use of torture in prosecutions for witchcraft (approximate date).