Emperor Theodosius I, also known as Theodosius the Great, ruled the Roman Empire from 379 to 395 AD. He was the last emperor to govern both the eastern and western halves of the empire. Theodosius is known for making Christianity the official state religion and for suppressing pagan practices, which significantly shaped the religious landscape of the empire. During his reign, Theodosius faced various challenges, including conflicts with the Goths and other barbarian tribes. He is remembered for his efforts to maintain stability within the empire and for his role in the First Council of Constantinople in 381 AD, which further defined Christian doctrine.