816

Year 816 was a leap year starting on Tuesday of the Julian calendar, the 816th year of the Common Era and Anno Domini designations, the 816th year of the 1st millennium, the 16th year of the 9th century, and the 7th year of the 810s decade.

Events

October 5 - King Louis the Pious is crowned emperor of the Holy Roman Empire, by Pope Stephen IV at Reims. He also crowns the emperor's wife Ermengarde as Holy Roman Empress. The ceremony in Reims re-establishes the principle of papal supremacy, by recognising the importance of the pope in imperial coronations. Louis gives the pope many gifts, including the estate tax Vendeuvre, near Troyes.
Vikings raid Ireland at the Kingdom of Munster, at Inish Cathaigh.
Battle of Pancorbo: A Moorish army from the Emirate of Córdoba is sent by Emir Al-Hakam I, to take control of the pass at Pancorbo. They defeat the army of Asturian-Basque Frankish vassals.
Winter - The Basques, supported by the Moors, cross the Garonne River and revolt against the Franks in Gascony.
Britain
King Hywel of Gwynedd is attacked by his brother Cynan on Anglesey, who is killed during the fighting.
Abbasid Caliphate
Babak Khorramdin, Persian military leader, revolts against the Abbasid Caliphate in Azerbaijan.
By topic

Synod of Aachen: Louis the Pious calls for a council about the regulations for monastic life in the Frankish Empire.
Synod of Chelsea: King Coenwulf of Mercia calls for a council about his right to appoint abbots and monasteries in England.
June 12 - Pope Leo III dies after a 20-year reign, and is succeeded by Pope Stephen IV as the 97th pope of Rome.