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 had been invited to help on orders by Emir Abbad III.
• Norman forces under Count Roger I conquer Syracuse, the last Muslim stronghold in Sicily.

  England

• August 1 - King William I calls for a meeting at Old Sarum, where he invites his major vassals and tenants-in-chief to swear allegiance to him. The oath is known as the Oath of Salisbury.
• The Domesday Book is completed, which is 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 Rum Sultanate, is killed by Emir Tutush I near Antioch. Suleiman's 7-year-old son Kilij Arslan 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.