Russian Empire
Though the Empire was only officially proclaimed by Tsar Peter I following the Treaty of Nystad (1721), some historians would argue that it was truly born either when Ivan III of Russia conquered Veliky Novgorod in 1478, or when Ivan the Terrible conquered the Khanate of Kazan in 1552. According to another point of view, the term "Tsardom", which was used after the coronation of Ivan IV in 1547, was already a contemporary Russian word for empire.
Romanov Empire (micronation)
Bakov declared the new Russian Empire to be the successor to the historical Russian Empire that ceased to exist in 1917. The Imperial Throne also claimed the right to maritime territories that were either claimed by the Russian Empire or discovered by the Imperial Russian Navy but never absorbed into the Soviet Union. The 17 claimed territories include the entire continent of Antarctica and land under the jurisdiction of Japan, the United Kingdom, the United States, and other nations.