1011

By place

Europe

• June 11 - Lombard Revolt: Mahmoud the Fat of Bari rises up against the Lombard rebels, led by Melus, and delivers the city to Basil Mesardonites, Byzantine governor of the Catepanate of Italy. Melus is forced to flee to Salerno, and his brother-in-law Dattus escapes to Monte Cassino, but their families are taken captive, and carted off to Constantinople.
• Autumn - Basil Mesardonites visits Guaimar III of Salerno to secure his cooperation. Melus is forced to flee again. Basil proceeds to Monte Cassino – and persuades Abbot Atenulf to expel Dattus. Pope Sergius IV supports Dattus with papal troops, to garrison the tower on the Garigliano River, a fortified complex in the territory of the Duchy of Gaeta.
• King Henry II enfeoffs Adalbero with Carinthia after the death of Duke Conrad I.
• The Grand Prince of Kyiv and ruler of Kievan Rus' Vladimir the Great laid the first foundations of Saint Sophia Cathedral, Kyiv.

England

• September 29 - Siege of Canterbury: Danish Viking raiders led by Thorkell the Tall pillage Canterbury after a siege, taking Ælfheah, archbishop of Canterbury, as a prisoner.
• Byrhtferth, Benedictine monk of Ramsey Abbey, writes his Manual on the divine order of the universe and time.

Middle East

• Ibn al-Haytham, an Arab scientist working in Egypt, feigns madness for fear of angering Caliph Al-Hakim bi-Amr Allah, and is kept under house arrest. During this time he begins writing his influential Book of Optics.
• The Baghdad Manifesto is ordered by Caliph Al-Qadir of the Abbasid Caliphate, in response to the growth of the Fatimid-supporting Ismaili sect of Islam within his borders.

Asia

• Emperor Ichijō abdicates the throne and dies later after a 25-year reign. He is succeeded by his cousin Sanjō as the 67th emperor of Japan.