A Tetrarch was a ruler of one of four divisions of a region in ancient Rome, particularly during the late Roman Empire. The term is derived from the Greek word "tetrarchēs," meaning "ruler of a quarter." The most notable use of the title occurred during the reign of Emperor Diocletian, who established the Tetrarchy in 293 AD to improve governance and stability across the vast empire. Under the Tetrarchy, the Roman Empire was divided into four regions, each governed by a Tetrarch. This system aimed to address the challenges of managing a large empire by delegating authority and ensuring more localized control. The Tetrarchs were typically composed of two senior emperors, known as Augusti, and two junior emperors, called Caesares.