1. Mehmed VI
Mehmed VI was the last Sultan (Emperor) of the Ottoman Empire who reigned from 1918 to 1922. In 1922, the Ottoman Sultanate (Empire) was abolished after the First World War and Mehmed VI stepped down as the emperor. The Sultanate was then superseded by the Republic of Turkey in 1923.
2. Napoleon III
Napoleon III was the last Emperor of the French who reigned from 1852 to 1870. After serving as the first President of France from 1848 to 1852, Napoleon III seized power by force as he could not be reelected constitutionally. He then proclaimed himself Emperor and founded the Second Empire. He reigned as the Emperor of the French until the French Army was defeated by Prussia and its allies in 1870 at the Battle of Sedan.
3. Romulus Augustus
Romulus Augustus was the last Roman emperor of the West. In 475, Augustus was placed on the throne by his father Orestes. As Augustus was still a minor, he only served as a figurehead for Orestes due to political reasons. Just ten months into his reign, barbarian general Flavius Odoacer killed Orestes and dethroned Romulus Augustulus. His deposition marked the political fall of the Western Roman Empire as Odoacer did not officially announce any successor.
4. Wilhelm II
Wilhelm II was the last German Emperor who reigned from 1888 until his abdication in 1918. His abdication, which was brought about by a series of German defeats in the First World War, brought an end to a three-hundred-year reign of the House of Hohenzollern. After his abdication, the monarchy was abolished and Germany was converted into a democratic state, which came to be known as the Weimar Republic.
Francis II, Holy Roman Emperor was the last Holy Roman Emperor who reigned from 1792 to 1806. In 1806, Francis abdicated as Holy Roman Emperor after the creation of the Confederation of the Rhine by Napoléon Bonaparte. The War of the Third Coalition brought about the Treaty of Pressburg which in turn brought about the fall of the Holy Roman Empire.