1089

By place

Europe

• King Demetrius Zvonimir of Croatia dies after a 12-year reign, and is succeeded by Stephen II. Zvonimir's widow, Queen Helena plots the inheritance of the Croatian crown for her brother, King Ladislaus I of Hungary.
• June 24 - Viscount Gaston IV of Béarn reconquers the Aragonese city of Monzón, from Emir Al-Mustain II of the Taifa of Zaragoza.
• August 18 - Emperor Henry IV marries Eupraxia at Cologne. She is crowned and assumes the name Adelaide.
• King George II abdicates the throne in favor of his 16-year-old son David IV who becomes ruler of Georgia.

  England

• Northumbria is divided by King William II into the counties of Northumberland, County Palatine of Durham, Yorkshire, Westmorland and Lancashire.
• August 11 - A powerful earthquake is recorded in England.

  By topic

Religion

• March 21 - Cîteaux Abbey, the first Cistercian monastery, is established by a group of French monks under Robert of Molesme in southern France.
• September - The Synod of Melfi led by Pope Urban II issues decrees against simony and clerical marriage.
• September - A church council, held in Constantinople discuses relations between Eastern and Western Christianity.