Basil II Porphyrogenitus (Greek: Βασίλειος Πορφυρογέννητος, romanized: Basíleios Porphyrogénnētos; 958 – 15 December 1025), nicknamed the Bulgar Slayer (Greek: ὁ Βουλγαροκτόνος, ho Boulgaroktónos, Bulgarian: Българоубиец), was the senior Byzantine emperor from 976 to 1025. He and his brother Constantine VIII were crowned before their father Romanos II died in 963, but they were too young to rule. The throne thus went to two generals, Nikephoros Phokas (r. 963–969) and John Tzimiskes (r. 969–976) before Basil became senior emperor, though his influential great-uncle Basil Lekapenos remained as the de facto ruler until 985. His reign of 49 years and 11 months was the longest of any Roman emperor.
The early years of Basil's reign were dominated by civil wars against two powerful generals from the Byzantine Anatolian aristocracy: first Bardas Skleros and later Bardas Phokas, which ended shortly after Phokas' death and Skleros' submission in 989. Basil then oversaw the stabilization and expansion of the eastern frontier of the Byzantine Empire and the complete subjugation of the First Bulgarian Empire, its foremost European foe, after a long struggle. Although the Byzantines had made a truce with the Fatimid Caliphate in 987–988, Basil led a campaign against the Caliphate that ended with another truce in 1000. He also conducted a campaign against the Khazar Khaganate that gained the Byzantine Empire part of Crimea and a series of successful campaigns against the Kingdom of Georgia.