Marcellus I was the bishop of Rome from 308 until his death in 309. Following the intense persecutions of the Diocletian era, he worked to reorganize the local church, which had been left in significant disorder. He divided the city into twenty-five administrative districts, known as tituli, to better manage baptisms, penance, and burials. His leadership was marked by strictness regarding the readmission of Christians who had lapsed during previous persecutions, a stance that eventually led to his exile and death.