Year 990 (CMXC) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar.
Events
By place
Europe
Al-Mansur, Chancellor and effective ruler of Al-Andalus, conquers the Castle of Montemor-o-Velho (modern Portugal), expanding the Umayyad Caliphate of Córdoba.
The city of Lund, Sweden is founded, during the reign of the Danish king Sweyn Forkbeard (approximate date).
Africa
The Ghana Empire takes the Berber town of Aoudaghost (modern Mauritania) as the West African nation makes further gains.
Construction of the Al-Hakim Mosque by orders of the Fatimid vizier Gawar Al-Siqilli begins in Cairo (modern Egypt).
By topic
Religion
June – The Pax Ecclesiae, an edict by the Catholic Church, is promulgated. Held at three synods in different parts of southern and central France (at Charroux, Narbonne and Puy), it attempts to outlaw acts of war against non-combatants and the clergy.
Births
November 11 – Gisela of Swabia, Holy Roman Empress (d. 1043)
Adamo Abate, Italian Benedictine abbot (approximate date)
Al-Qadi Abu Ya'la, Arab Hanbali scholar and jurist (d. 1066)
Bi Sheng, Chinese inventor of movable type printing (d. 1051)
Chananel ben Chushiel, Tunisian Jewish rabbi (d. 1053)
Conrad II (the Elder), Holy Roman Emperor (d. 1039)