Year 1011 (MXI) was a common year starting on Monday (link will display the full calendar) of the Julian calendar.
The Chinese Guangyun rime dictionary is compiled under Emperor Zhenzong of Song.
Emperor Sanjō ascends to the throne of Japan.
Baghdad Manifesto: Al-Hakim bi-Amr Allah's descent from Ali ibn Abi Talib is disputed.
Ibn al-Haytham (Alhazen), a famous Persian scientist working in Egypt, feigns madness for fear of angering Al-Hakim, and is kept under house arrest until 1021. During this time he begins writing his influential Book of Optics.
In Georgia, Bagrat III dispossesses Sumbat III of Klarjeti, who dies thereafter.
June 11 – The Byzantine army, under the catapan Basil Mesardonites, takes Bari from the rebellious Lombard lord Melus.
September 29 – Danes capture Canterbury after a siege, taking Ælfheah, Archbishop of Canterbury, as a prisoner.
Ermengol II succeeds Ermengol I, as Count of Urgell.
Albert II, Count of Namur succeeds Albert I.
The German king Henry II enfeoffes Adalbero, Duke of Carinthia with the Carinthian duchy, including the rule over the March of Verona (or in 1012).
Byrhtferth, of Ramsey Abbey in England, writes his Manual (Enchiridion) on the divine order of the universe and time.
Eleanor of Normandy, a Norman noblewoman and the daughter of Richard II of Normandy (possible date; d. after 1071)
Ralph the Staller, earl of East Anglia (d. 1068)
Robert I, Duke of Burgundy (d. 1076)
Shao Yong, Song Dynasty philosopher, cosmologist, poet and historian (d. 1077)
February 23 – Willigis, Archbishop of Mainz and a statesman of the Holy Roman Empire (b. c. 940)
November 21 – Emperor Reizei of Japan (b. 950)
Conrad I, Duke of Carinthia (b. c. 975)
Emperor Ichijō of Japan (b. 980)
Albert I, Count of Namur (b. c. 950)
Armentarius, Galician bishop (b. 983)
Sumbat III of Klarjeti, Georgian prince of the Bagratid dynasty of Tao-Klarjeti and the last sovereign of Klarjeti
Yohannan V, Patriarch of the Church of the East
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