|Covid-19|September – Emperor Michael III is murdered, by order of his co-emperor Basil I. Basil becomes sole ruler (basileus) of the Byzantine Empire, and founds the Macedonian Dynasty (until 1056). Basil rebuilds the Byzantine army and navy, in an effort to restore the empire.
August – Treaty of Compiègne: King Charles the Bald cedes the Cotentin Peninsula to Salomon, duke ('king') of Brittany, after he had sent his son-in-law Pascweten to negotiate a peace. Charles orders the fortification of the cities of Tours, Le Mans and Compiègne.
Bořivoj I declares himself duke (knyaz) of Bohemia, and founds the Pŕemyslid Dynasty (approximate date).
The rival monarchs, Ælla and Osberht of Northumbria, join forces to expel the Great Heathen Army, but are defeated in battle by Ivar the Boneless and Halfdan Ragnarsson. Osberht is killed, while Ælla is executed by the traditional Viking way of the blood eagle.
Danish Vikings conquer Deira in Northern England; the Northumbrian royal court flees into Bernicia. Ivar the Boneless installs Ecgberht I, as a puppet king.
September – Photius I ("the Great"), patriarch of Constantinople, is removed from office and banished. Ignatius is reinstated as patriarch by Basil I.
November 13 – Pope Nicholas I dies after a 9-year reign. He is succeeded by Adrian II (also referred to as Hadrian II), as the 106th pope of Rome.
June 10 – Uda, emperor of Japan (d. 931)
October 10 – Li Siyuan, emperor of Later Tang (d. 933)
Gyeon Hwon, king of Hubaekje (Korea) (d. 936)
Pribislav, prince (knyaz) of Serbia (approximate date)
Stephen I, patriarch of Constantinople (d. 893)
Zhao Zong, emperor of the Tang Dynasty (d. 904)
Zhu Jin, Chinese warlord (d. 918)
March 21 – Ælla, king of Northumbria
March 21 – Osberht, king of Northumbria
November 13 – Nicholas I, pope of the Catholic Church
Auisle, Viking leader (approximate date)
Cormac mac Connmhach, Irish monk and scribe
Donnchad mac Aedacain, king of Uisneach (Ireland)
Eahlstan, bishop of Sherborne
Fujiwara no Yoshimi, Japanese nobleman (b. 813)
Fujiwara no Yoshisuke, Japanese statesman (b. 813)
Galindo Aznárez I, count of Aragon
Gottschalk of Orbais, German monk and theologian
Lazarus Zographos, Byzantine monk and painter
Louis, Frankish archchancellor and abbot
Michael III, emperor of the Byzantine Empire (b. 840)
Muhammad ibn Abdallah, Abbasid governor
Qarin I, ruler (spahbed) of the Bavand Dynasty
Wasif al-Turki, Abbasid general
Wulfsige, bishop of Lichfield
Year 867 (DCCCLXVII) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar.