Vikings known as Rus' (Norsemen) plunder the north coast of Anatolia (modern Turkey), marking the first recorded raid of Rus' people or Russians, on territory in the Byzantine Empire.
April 17 – King Bernard of Italy, illegitimate son of Pepin of Italy, is tried and condemned to death by Emperor Louis I. The Kingdom of Italy is reabsorbed into the Frankish Empire.
The Slavs on the Timok River break their alliance with the Bulgars. Duke Ljudevit of Pannonian Croatia sends emissaries to Louis I, to assert his independence from the Franks.
Al-Andalus: A grave rebellion breaks out in the suburbs of Cordoba, against the Umayyad Caliphate. Andalucian Arab refugees arrive in Fez (modern Morocco).
The Anglo-Saxons, led by King Coenwulf of Mercia, raid Dyfed in Wales (approximate date).
Beginning of the Lemro period: The Sambawa and Pyinsa Kingdoms are founded in present-day Myanmar.
Theodulf, bishop of Orléans, is deposed and imprisoned, after becoming involved in a conspiracy with Bernard of Italy.
Abu Dawud, Muslim hadith compiler (or 817)
Al-Fath ibn Khaqan, Muslim governor (or 817)
Ariwara no Yukihira, Japanese governor (d. 893)
Pepin, count of Vermandois (approximate date)
Sahl al-Tustari, Persian scholar (approximate date)
April 17 – Bernard of Italy, king of the Lombards (b. 797)
October 3 – Ermengarde, queen of the Franks
Al-Fadl ibn Sahl, Persian vizier
Ali al-Ridha, 8th Shia Imam (b. 766)
Cernach mac Congalaig, king of Brega (Ireland)
Clement, Irish scholar and saint
Felix, bishop of Urgell (Spain)
García I Jiménez, duke of Gascony
Hildebold, archbishop of Cologne
Michael the Confessor, bishop of Synnada
Morman, chieftain and king of Brittany
Muiredach mac Brain, king of Leinster (Ireland)
Theophanes the Confessor, Byzantine monk (or 817)
Quan Deyu, chancellor of the Tang Dynasty (b. 759)
Yuan Zi, general of the Tang Dynasty (b. 739)
Year 818 (DCCCXVIII) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.