|Centuries:||7th century – 8th century – 9th century|
|Decades:||750s 760s 770s – 780s – 790s 800s 810s|
|Years:||783 784 785 – 786 – 787 788 789|
|786 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1539|
|Chinese calendar||乙丑年 (Wood Ox)
3482 or 3422
— to —
丙寅年 (Fire Tiger)
3483 or 3423
|- Vikram Samvat||842–843|
|- Shaka Samvat||708–709|
|- Kali Yuga||3887–3888|
|Japanese calendar||Enryaku 5
|Minguo calendar||1126 before ROC
|Seleucid era||1097/1098 AG|
|Thai solar calendar||1328–1329|
Year 786 (DCCLXXXVI) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar. The denomination 786 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
- King Charles the Younger, son of Charlemagne and ruler of Aquitaine, visits Monte Cassino and Capua, both in Beneventan territory. Prince Arechis II signs an agreement with the neighbouring Byzantine Duchy of Naples called a 'pactum'.
- Cyneheard, brother of the late king Sigeberht, ambushes and kills his rival Cynewulf of Wessex while he is at Meretun (now called Marten) with his mistress. The Wessex nobles refuse to recognise Cyneheard as king.
- Cyneheard is executed and succeeded by Beorhtric through support of king Offa of Mercia. His rival claimant to the Wessex throne, a distant nephew of the late king Ine named Egbert, is driven across the Channel.
- Egbert settles at the court of Charlemagne and learns the arts of government during his time in Gaul. During his stay he meets Eadberht, a priest, who becomes later king of Kent.
- June 11 – Battle of Fakhkh: A Hasanid Alid uprising in Mecca is crushed by the Abbasids. One of the Alids, Idris ibn Abdallah, flees to the Maghreb in western North Africa, where he later founds the Idrisid dynasty.
- September 14 – Harun al-Rashid becomes the Abbasid caliph in Baghdad upon the death of his brother Al-Hadi. He appoints Salim Yunisi as governor of Sindh and the Indus Valley.
- Al-Ḥajjāj ibn Yūsuf ibn Maṭar, Muslim mathematician (d. 833)
- Al-Ma'mun, Muslim caliph (d. 833)
- Saga, emperor of Japan (d. 842)
- Tachibana no Kachiko, empress of Japan (d. 850)
- Abo of Tiflis, Christian martyr
- Al-Rabi' ibn Yunus, Muslim minister (or 785)
- September 14 – Al-Hadi, Muslim caliph (b. 764)
- Cyneheard the Ætheling, nobleman of Wessex
- Cynewulf, king of Wessex
- Desiderius, king of the Lombards (approximate date)
- Diarmait mac Conaing, king of South Brega (Ireland)
- October 16 – Lullus, archbishop of Mainz
- Sakanoue no Karitamaro, Japanese general (b. 727)
- Tipraiti mac Taidg, king of Connacht (Ireland)
- Kirby, Earliest English Kings, pp. 176-177