A proconsul was a Roman official tasked with acting on behalf of a consul, a role that evolved significantly between the Republic and the Empire. In the Roman Republic, the office was essential for maintaining military command, known as imperium, which was constitutionally restricted to consuls.
Because consuls served only one-year terms and were prohibited from consecutive re-election, the practice of prorogation was developed. This allowed a consul's command to be extended, ensuring continuity during ongoing military campaigns. In contrast, during the Roman Empire, the title of proconsul was repurposed to designate a civil governor, stripped of its original military command authority.