Ivan IV Vasilyevich (3 September [O.S. 25 August] 1530 – 28 March [O.S. 18 March] 1584), commonly known as Ivan the Terrible or Ivan the Fearsome, was the Grand Prince of Moscow from 1533 to 1547 and 'Tsar of All the Russias' from 1547 until his death in 1584.

His long reign saw the conquest of the Khanate of Kazan, Khanate of Astrakhan and Khanate of Sibir, transforming Russia into a multiethnic and multicontinental state spanning almost one billion acres, approximately 4,050,000 km2 (1,560,000 sq mi). Ivan managed countless changes in the progression from a medieval state to an empire and emerging regional power, and became the first ruler to be crowned as Tsar of All the Russias.

Historic sources present disparate accounts of Ivan's complex personality: he was described as intelligent and devout, yet given to rages and prone to episodic outbreaks of mental instability.

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