|859 by topic|
|Ab urbe condita||1612|
|Balinese saka calendar||780–781|
|Chinese calendar||戊寅年 (Earth Tiger)|
3556 or 3349
— to —
己卯年 (Earth Rabbit)
3557 or 3350
|- Vikram Samvat||915–916|
|- Shaka Samvat||780–781|
|- Kali Yuga||3959–3960|
|Japanese calendar||Ten'an 3 / Jōgan 1|
|Minguo calendar||1053 before ROC|
|Seleucid era||1170/1171 AG|
|Thai solar calendar||1401–1402|
985 or 604 or −168
— to —
986 or 605 or −167
- January 15 – Battle of St. Quentin: Frankish forces, led by Humfrid, defeat King Louis the German at Saint-Quentin (Northern France). Humfrid is enfeoffed with the County of Autun, and appointed Margrave of Burgundy, by King Charles the Bald.
- Summer – The Viking chieftains Hastein and Björn Ironside (a son of Ragnar Lodbrok) begin an expedition, and sail from the Loire River with a fleet of 62 ships, to raid cities and monasteries in the Mediterranean Sea.
- Viking raiders invade the Kingdom of Pamplona (Western Pyrenees), and capture King García Íñiguez I, somewhere in the Andalusian heartland. They extort a ransom, rising to around 70,000 gold dinars.
- The Russian city of Novgorod is first mentioned in the Sofia Chronicles.
- Winter – The weather is so severe that the Adriatic Sea freezes, and Italy is covered in snow for 100 days.
- Battle of Albelda: King Ordoño I of Asturias, and his ally García Íñiguez I, defeat the Muslims under Musa ibn Musa al-Qasawi at Albelda.
- Viking raiders burn the mosques of Seville and Algeciras in al-Andalus (modern Spain).
- The University of Al Karaouine is founded in Fes (modern Morocco), by Fatima al-Fihri (recognized by the Guinness Book of World Records as the oldest university in the world).
- September 7 – Emperor Xuān Zong (Li Yi) dies after a 13-year reign. He is succeeded by his eldest son Yi Zong, as ruler of the Tang dynasty.
- 859 Syrian coast earthquake. It affected the Mediterranean coast of Syria It caused almost the complete destruction of Latakia and Jableh, major damage at Antioch and led to many deaths.
- Al-Hadi ila'l-Haqq Yahya, first Zaydi Imam of Yemen (d. 911)
- Ali ibn Isa al-Jarrah, vizier of the Abbasid Caliphate (d. 946)
- Odo I, king of the West Frankish Kingdom (or 860)
- Rudolph I, king of Burgundy (d. 912)
- Tannet of Pagan, king of Burma (d. 904)
- September 7 – Xuān Zong, emperor of the Tang dynasty (b. 810)
- December 13 – Angilbert II, archbishop of Milan
- Dhul-Nun al-Misri, Egyptian scholar and Sufi (b. 796)
- Immo, bishop of Noyon (approximate date)
- Lu Shang, chancellor of the Tang dynasty (b. 789)
- Máel Gualae, king of Munster (Ireland)
- Haywood, John (1995). The Historical Atlas of the Vikings, pp. 58–59. Penguin Books: ISBN 0-14-051328-0
- Martínez Díez 2007, p. 25.
- Yanko-Hombach, Valentina (2006). The Black Sea Flood Question. Springer. p. 638. ISBN 1402047746.
- Rucquoi, Adeline (1993). Histoire médiévale de la Péninsule ibérique. Paris: Seuil. p. 85. ISBN 2-02-012935-3.
- Antonopoulos, J. (1980). "Data from investigation of seismic Sea waves events in the Eastern Mediterranean from 500 to 1000 A.D.". Annals of Geophysics. 33 (1). doi:10.4401/ag-4701.
- Ambraseys, N. (2009). Earthquakes in the Mediterranean and Middle East: A Multidisciplinary Study of Seismicity up to 1900 (First ed.). Cambridge University Press. pp. 243–244. ISBN 978-1-316-34785-0.
- Madelung, W. (2004). "al-Ḥādī Ila 'l-Ḥaḳḳ". In Bearman, P. J.; Bianquis, Th.; Bosworth, C. E.; van Donzel, E. & Heinrichs, W. P. (eds.). Encyclopaedia of Islam. Volume XII: Supplement (2nd ed.). Leiden: E. J. Brill. pp. 334–335. ISBN 978-90-04-13974-9.