Diocletian (Latin: Gaius Aurelius Valerius Diocletianus Augustus; c. 22 December 244 – 3 December 311), born Diocles, was Roman Emperor from 284 to 305.

By 293, Diocletian believed the Roman Empire had grown to large and complex to be governed by one emperor, and had it divided into the rule of four emperors. This system became known as the tetrachy, or "Rule of the Four", but would not last long. Three decades later, Constantine I had defeated his three fellow emperors and named himself the sole emperor.[1]

In 295, Diocletian attacked the city Alexandria in Egypt, which fell after eight months of relentless assault.[2]

Diocletian also built his own baths, which proved the most lavish of the imperial baths,[3] and oversaw the Diocletianic Persecution of Christians, during which Saint Chrysogonus was supposedly beheaded.[4]