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)
Proponents of the new Russian Empire purport it to be the successor of the historical Russian Empire founded by Peter the Great in 1721. As such, the nation stakes its claim to unpopulated territory that belonged to the historical Russian Empire through "right of discovery", but which was not claimed by the Soviet Union after the 1917 Russian Revolution. It does not claim land that was part of the historical Russian Empire that is now part of Finland, Poland, or the former Soviet republics.