Roman Republic
Some people say the Roman Republic ended with the naval Battle of Actium between Marcus Antonius and Octavian. Both had been in the Second Triumvirate. The battle was fought on 2 September 31 BC in which Octavian won. Later, he was proclaimed Roman emperor. The end date could also be when Octavian was given the title of the first Augustus by the Senate, on 16 January 27 BC.