1086

By place

Europe

• October 23 - Battle of Sagrajas: Spanish forces under King Alfonso VI of Castile are defeated by the Moors and their allies, the Almoravids, who have been invited to help on orders by Emir Al-Mu'tamid ibn Abbad.
• Siege of Syracuse (1086) - Norman forces under Count Roger I conquer Syracuse, the last Muslim stronghold in Sicily.

England

• August 1 - King William the Conqueror calls for a meeting at Old Sarum, where he invites his major vassals and tenants-in-chief to swear allegiance to him. This is known as the Oath of Salisbury.
• The Domesday Book is completed. Drawn up on the orders of William I; it describes in detail the landholdings and resources in England.
• The population in England is estimated to be 1.25 million citizens with 10% living in boroughs.

Seljuk Empire

• Summer - Suleiman ibn Qutulmish, ruler of the Turks in Rum, is killed by Emir Tutush I in the battle of Ain Salm near Antioch. Suleiman's 7-year-old son Kilij Arslan I is captured and transferred as hostage to Isfahan.
• Sultan Malik-Shah I rebuilds the Imam Ali Mosque in Najaf, after it was destroyed by fire.

By topic

Religion

• May 24 - Pope Victor III succeeds Gregory VII as the 158th pope of the Catholic Church, though he does not accept election until 1087.

Births

• April 24 - Ramiro II, king of Aragon
• August 11 - Henry V, Holy Roman Emperor
• August 20 - Bolesław III Wrymouth, duke of [Kingdom of Kingdom of Poland (1025–1385)|Poland (1025–1385)|Poland]
• al-Shahrastani, Persian scholar and historian
• Þorlákur Runólfsson, Icelandic bishop
• Vicelinus, bishop of Oldenburg in Holstein
• Zhang Jun, Chinese general and official

Deaths

• March 15 - Richilde, countess and regent of Flanders
• March 18 - Anselm of Lucca, Italian bishop
• May 21 - Wang Anshi, Chinese chancellor
• July 10 - Canute IV, king of Denmark
• July 14 - Toirdelbach Ua Briain, Irish king
• July 17 - García Ramírez, Aragonese bishop
• August 8 - Conrad I, count of Luxembourg
• September 25 - William VIII, duke of Aquitaine
• October 11 - Sima Guang, Chinese politician
• October 23 - Rodrigo Muñoz, Galician nobleman
• December 25 - Judith of Bohemia, duchess of Poland
• Gregory Pakourianos, Byzantine politician and general, killed in battle
• Huizong, Chinese emperor
• Mael Ísu Ua Brolcháin, Irish monk and writer
• Muhammad ibn Ammar, Moorish poet
• Odo I of Furneaux, French nobleman
• Suleiman ibn Qutulmish, ruler of the Sultanate of Rum, killed in battle