In ancient Rome, any of various high officials with primarily judicial and administrative responsibilities. In the early republic, a prefect of the city (praefectus urbi) took over the consul's duties during their absence from Rome. The office lost some importance after the introduction of praetors (mid 4th century BC). Augustus revitalized the office when he appointed five prefects to supervise the city government, the fire brigade, the grain supply, and the Praetorian Guard. The praetorian prefects acquired great power and often became virtual prime ministers.