841

By place

Europe

• June 25 - Battle of Fontenay: Frankish forces of Emperor Lothair I, and his nephew Pepin II of Aquitaine, are defeated by allied forces of King Louis the German, and his half-brother Charles the Bald, at Fontenoy, in a civil war among the three surviving sons of the former emperor Louis the Pious. A total of 40,000 men are killed, including the Frankish nobles Gerard of Auvergne and Ricwin of Nantes, fighting on the side of Charles.
• Summer - Vikings sail up the River Seine and devastate the city of Rouen in Normandy. They burn the Benedictine monastery of Jumièges Abbey; 68 captives are taken, and returned on payment of a ransom, by the monks of St. Denis.

  Ireland

• The town of Dyflin or Dublin is founded by Norwegian Vikings, on the south bank of the River Liffey. The settlement is fortified with a ditch and an earth rampart, with a wooden palisade on top. The Norsemen establish a wool weaving industry, and there is also a slave trade. An artificial hill is erected, where the nobility meets to make laws and discuss policy.

  Byzantine Empire

• Constantine Kontomytes, Byzantine general of the Thracesian Theme, inflicts a severe defeat on the Cretan Saracens. He leads a Byzantine expeditionary force, to raid the monastic community near Mount Latros.
• Venice sends a fleet of 60 galleys to assist the Byzantines in driving the Arabs from Crotone, but the attack fails. Muslim troops conquer the city of Brindisi.

  Abbasid Caliphate

• A pro-Umayyad rebellion, led by al-Mubarqa in Palestine, breaks out against caliph al-Mu'tasim of the Abbasid Caliphate.

  Asia

• In the Chinese capital of Chang'an, the West Market are closed every night one hour and three quarters before dusk ; the curfew is signaled by the sound of 300 beats to a loud gong. After the official markets have been closed for the night, small night markets in residential areas thrive with plenty of customers, despite government efforts to shut them down. With the decline of the government's authority, this edict is largely ignored, as urban dwellers keep attending the night markets regardless.
• December 17 – Comet X/841 Y1 is first sighted in Chang'an by the Japanese monk Ennin.