Year 998 (CMXCVIII) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar.
Battle of Ghazni: Mahmud of Ghazni wins, and succeeds as the Amir of Ghazni.
June – Tyre is stormed by the forces of the Fatimid Caliphate, ending a two-year rebellion of its citizens.
19 July – Battle of Apamea: The Fatimid army, under Jaysh ibn Samsama, defeats and kills the Byzantine general Damian Dalassenos.
The Uji Villa is officially built by Michinaga Fujiwara, as predecessor of Byodo-in in Yamashiro Province, (present day of Kyoto Prefecture) Japan.
Otto III retakes the city of Rome, and reinstates his cousin, Pope Gregory V, after mutilating and blinding his rival, Antipope John XVI.
St. Volodimir of Rus founds (or, according to some documents, gives his name to) the city of Volodimir of Wolyn, future capital of the kingdom of Ruthenia Minor (Halych-Wolyn Rus).
Emperor Samuil of Western Bulgarian Tsardom launches a military campaign against Kingdom of Croatia, and besieges the city of Zadar.
A Benedictine abbey is founded at Sherborne.
St. Volodimir, Prince of Kiev Rus (modern Ukraine, Russia and Belarus), baptizes his country.
George I of Georgia
Abu'l-Wafa, Iranian mathematician
July 19 – Damian Dalassenos, Byzantine duke of Antioch
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