Consul, in Roman history, a head magistrate, or executive, in the Republic. There were two consuls, elected annually by the centurial assembly (one of four Roman legislatures). They had complete authority over both civil affairs and military matters, but could act only in unison. As Rome expanded its territory, an executive called a proconsul, who had the power of a consul, was chosen to rule in each overseas province. Proconsuls were often former consuls and as heads of provincial armies often possessed great power.