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.
Russian Empire
By the end of the 19th century the size of the empire was about or almost 1/6 of the Earth's landmass; its only rival in size at the time was the British Empire. However, at this time, the majority of the population lived in European Russia. More than 100 different ethnic groups lived in the Russian Empire, with ethnic Russians composing about 45% of the population.