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.
History of the Roman Empire
The period of the "Five Good Emperors" was brought to an end by the reign of Commodus from 180 to 192. Commodus was the son of Marcus Aurelius, making him the first direct successor in a century, breaking the scheme of adoptive successors that had worked so well. He was co-emperor with his father from 177. When he became sole emperor upon the death of his father in 180, it was at first seen as a hopeful sign by the people of the Roman Empire. Nevertheless, as generous and magnanimous as his father was, Commodus was just the opposite. In "The Decline and Fall of the Roman Empire" by Edward Gibbon, it is noted that Commodus at first ruled the empire well. However, after an assassination attempt, involving a conspiracy by certain members of his family, Commodus became paranoid and slipped into insanity. The Pax Romana, or "Roman Peace", ended with the reign of Commodus. One could argue that the assassination attempt began the long decline of the Roman Empire. When Commodus' behaviour became increasingly erratic throughout the early 190s, Pertinax is thought to have been implicated in the conspiracy that led to Commodus' assassination on 31 December 192. The plot was carried out by the Praetorian prefect Quintus Aemilius Laetus, Commodus' mistress Marcia, and his chamberlain Eclectus.