Leo I (pictured), who ruled for nearly 20 years, was crowned Byzantine emperor.

Leo I, also known as "the Thracian", was Eastern Roman emperor from 457 to 474. He was a native of Dacia Aureliana near historic Thrace. He is sometimes surnamed with the epithet "the Great", probably to distinguish him from his young grandson and co-augustus Leo II.

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'.