Constantine VIII became the sole Byzantine emperor, 63 years after being crowned co-emperor.

Constantine VIII was de jure Byzantine emperor from 962 until his death. He was the younger son of Emperor Romanos II and Empress Theophano. He was nominal co-emperor from 962, successively with his father; stepfather, Nikephoros II Phokas; uncle, John I Tzimiskes; and brother, Basil II. Basil's death in 1025 left Constantine as the sole emperor. He occupied the throne for 66 years in total, making him de jure the longest-reigning amongst all Roman emperors since Augustus.

The Byzantine Empire, also known as the Eastern Roman Empire, was the continuation of the Roman Empire centred on Constantinople during late antiquity and the Middle Ages. Having survived the events that caused the fall of the Western Roman Empire in the 5th century AD, it endured until the fall of Constantinople to the Ottoman Empire in 1453. The term 'Byzantine Empire' was coined only after its demise; its citizens used the term 'Roman Empire' and called themselves 'Romans'.