AD 999

Events

King Bermudo II abdicates in favor of his 5-year-old son Alfonso V as ruler of León. Moorish invaders have forced Bermudo to recognize the suzerainty of their leader, Umayyad vizier and the de facto ruler Al-Mansur.
September 9 - Battle of Svolder: A Norwegian fleet, commanded by Olaf Tryggvason in his longship Ormrinn langi, is defeated by the combined fleet of the Danish king Sweyn Forkbeard and his Swedish counterpart Olof Skötkonung, resulting in Tryggvason's death, and the splitting up of Norway between Sweden and Denmark.

Ireland

December 30 – Battle of Glenmama: The combined forces of Munster and Meath under Brian Boru inflict a crushing defeat on the allied armies of Leinster and Dublin near Lyons Hill.

Central Asia

The Karakhanids invade from north of the Syr Darya river, ending the Samanid Empire. The Samanid domains are split between the Ghaznavid Dynasty and the Karakhanids.

Japan

February 9 – The Mogi Ceremony of Fujiwara no Shoshi is held.
December – Empress Teishi gives birth to Prince Atsuyasu, but on the next day, her rival, Fujiwara no Shoshi, is promoted to Consort.

Vietnam

Emperor Lê Đại Hành personally led a campaign to conquer a total of 49 tribes in Hà Động. The Nhật Tắc tribe and others in Định Biên province were defeated, while the remaining tribes capitulated to the emperor.

February 18 - Pope Gregory V dies after a 3-year pontificate in which the Crescentii family forced him to flee Rome. He is succeeded by Sylvester II as the 139th pope of the Catholic Church.
Bishop Aldhun consecrates a cathedral at a site in England where the remains of St. Cuthbert had been moved to in AD 995 from Lindisfarne because of the danger of Viking raids.
Sigmundur Brestisson, a Viking chieftain, introduces Christianity in the Faroe Islands.