Emperor
The first Austrian Emperor was the last Holy Roman Emperor Francis II. In the face of aggressions by Napoleon, Francis feared for the future of the Holy Roman Empire. He wished to maintain his and his family's Imperial status in the event that the Holy Roman Empire should be dissolved, as it indeed was in 1806 when an Austrian-led army suffered a humiliating defeat at the Battle of Austerlitz. After which, the victorious Napoleon proceeded to dismantle the old "Reich" by severing a good portion from the empire and turning it into a separate Confederation of the Rhine. With the size of his imperial realm significantly reduced, Francis II, "Holy Roman Emperor" became Francis I, "Emperor of Austria". The new imperial title may have sounded less prestigious than the old one, but Francis' dynasty continued to rule from Austria and a Habsburg monarch was still an emperor ("Kaiser"), and not just merely a king ("König"), in name.
Roman Republic
Since the foundation of Rome, its rulers had been monarchs, elected for life by the patrician noblemen who made up the Roman Senate. The last Roman king was Lucius Tarquinius Superbus ("Tarquin the Proud"). In the traditional histories, Tarquin was expelled in 509 because his son, Sextus Tarquinius, had raped the noblewoman Lucretia, who afterwards took her own life. Lucretia's father; her husband, Lucius Tarquinius Collatinus; and Tarquin's own nephew, Lucius Junius Brutus, mustered support from the Senate and army, and forced Tarquin into exile in Etruria.