|864 by topic|
|Ab urbe condita||1617|
|Balinese saka calendar||785–786|
|Chinese calendar||癸未年 (Water Goat)|
3560 or 3500
— to —
甲申年 (Wood Monkey)
3561 or 3501
|- Vikram Samvat||920–921|
|- Shaka Samvat||785–786|
|- Kali Yuga||3964–3965|
|Japanese calendar||Jōgan 6|
|Minguo calendar||1048 before ROC|
|Seleucid era||1175/1176 AG|
|Thai solar calendar||1406–1407|
990 or 609 or −163
— to —
991 or 610 or −162
Year 864 (DCCCLXIV) was a leap year starting on Saturday (link will display the full calendar) of the Julian calendar.
- Spring – Emperor Louis II (the Younger) marches with a Frankish army against Rome. While en route to the papal city, he becomes ill, and decides to make peace with Pope Nicholas I.
- July 25 – Edict of Pistres: King Charles the Bald orders defensive measures against the Vikings. He creates a large force of cavalry, which inspires the beginning of French chivalry.
- Viking raiders, led by Olaf the White, arrive in Scotland from the Viking settlement of Dublin (Ireland). He rampages the country, until his defeat in battle by King Constantine I.
- Robert the Strong, margrave of Neustria, attacks the Loire Vikings in a successful campaign. Other Viking raiders plunder the cities of Limoges and Clermont, in Aquitaine.
- King Louis the German invades Moravia, crossing the Danube River to besiege the civitas Dowina (identified, although not unanimously, with Devín Castle in Slovakia).
- Pepin II joins the Vikings in an attack on Toulouse. He is captured while besieging the Frankish city. Pepin is deposed as king of Aquitaine, and imprisoned in Senlis.
- September 13 – Pietro Tradonico dies after a 28-year reign. He is succeeded by Orso I Participazio, who becomes doge of Venice.
- King Alfonso III conquers Porto from the Emirate of Cordoba. This is the end of the direct Muslim domination of the Douro region.
- Mount Fuji, located on Honshu Island, erupts for 10 days, in an event known as the Jōgan eruption (Japan).
- Hasan ibn Zayd establishes the Zaydid Dynasty, and is recognized as ruler of Tabaristan (Northern Iran).
- The Christianization of Bulgaria begins: Boris I, ruler (khan) of the Bulgarian Empire, is converted to Orthodox Christianity. His family and high-ranking dignitaries accept the Orthodox faith at the capital, Pliska - from this point onwards the rulers of the Bulgarian Empire are known as ‘Tsars’ rather than ‘Khans’.
- Gu Quanwu, general of the Tang Dynasty (d. 931)
- Khumarawayh ibn Ahmad ibn Tulun, ruler of the Tulunid Dynasty (d. 896)
- Louis III, king of the West Frankish Kingdom (or 863)
- Muhammad ibn Ya'qub al-Kulayni, Muslim scholar (d. 941)
- Simeon I, ruler (khan) of the Bulgarian Empire (or 865)
- Yúnmén Wényǎn, Chinese Zen master (or 862)
- September 13 – Pietro Tradonico, doge of Venice
- Al-Fadl ibn Marwan, Muslim vizier
- Al-Fadl ibn Qarin al-Tabari, Muslim governor
- Arnold of Gascony, Frankish nobleman
- Bi Xian, chancellor of the Tang Dynasty (b. 802)
- Ennin, Japanese priest and traveler
- Hucbert, Frankish nobleman (b. 820)
- Laura, Spanish abbess
- Lorcán mac Cathail, king of Uisneach (Ireland)
- Muhammad ibn al-Fadl al-Jarjara'i, Muslim vizier (or 865)
- Pei Xiu, chancellor of the Tang Dynasty (b. 791)
- Sancho II, count of Gascony (approximate date)
- Sergius I, duke of Naples
- Trpimir I, duke (knez) of Croatia
- Yahya ibn Umar, Muslim imam (or 865)
- ^ Bowlus, Charles R. (1995). Franks, Moravians, and Magyars: The Struggle for the Middle Danube, 788-907 (Illustrated ed.). University of Pennsylvania Press, Incorporated. p. 140. ISBN 978-0-8122-3276-9.
- ^ Goldberg, Eric Joseph (2006). Struggle for Empire: Kingship and Conflict Under Louis the German, 817-876 (Illustrated, reprint ed.). Cornell University Press. p. 273. ISBN 978-0-8014-3890-5.
- ^ Picard, Christophe (2000). Le Portugal musulman (VIIIe-XIIIe siècle0. L'Occident d'al-Andalus sous domination islamique. Paris: Maisonneuve & Larose. p. 109. ISBN 2-7068-1398-9.
- ^ Buhl, Fr. (1986). Bearman, P.; Bianquis, Th.; Bosworth, C. E.; van Donzel, E.; Heinrichs, W. P. (eds.). "al-Ḥasan b. Zayd b. Muḥammad". The Encyclopaedia of Islam (2nd ed.). Brill: 245.
- ^ Karloukovski, Vassil (1927). "V. Zlatarski - Istorija 1 B - 3.2". Promacedonia.org. Retrieved August 26, 2017.