Leo I (Greek: Λέων Leōn; c. 401 – 18 January 474), also known as Leo the Thracian (Greek: Λέων ο Θραξ), was Eastern Roman emperor from 457 to 474. He was a native of Dacia Aureliana near historic Thrace. Sometimes, he is called Leo the Great (Greek: ὁ Μέγας, translit. ho Mégas), probably to distinguish him from his young grandson and co-augustus Leo II (Greek: ὁ Μικρός, translit. ho Mikrós, lit. "the Small").Ruling the Eastern Empire for nearly 20 years, Leo proved to be a capable ruler. He oversaw many ambitious political and military plans, aimed mostly at aiding the faltering Western Roman Empire and recovering its former territories. He is notable for being the first Eastern Emperor to legislate in Koine Greek rather than Late Latin. He is commemorated as a saint in the Eastern Orthodox Church, with his feast day on 20 January.