The Grand Duchy of Moscow (Russian: Великое Княжество Московское, Velikoye Knyazhestvo Moskovskoye), or Grand Principality of Moscow (also known in English simply as Muscovy), was a late medieval Rus' principality centered on Moscow and the predecessor state of the early modern Tsardom of Russia.
The state originated with Daniel I, who inherited Moscow in 1283, eclipsing and eventually absorbing its parent duchy of Vladimir-Suzdal by the 1320s. It later destroyed and annexed the Novgorod Republic in 1478 and the Grand Duchy of Tver in 1485. The Grand Duchy of Moscow expanded through conquest and annexation from just 20,000 square kilometers in 1300 to 430,000 in 1462, 2.8 million in 1533, and 5.4 million by 1584.
Muscovy remained a tributary to the Golden Horde (under the "Tatar Yoke") until 1480. Ivan III further consolidated the state during his 43-year reign, campaigning against his major remaining rival power, the Grand Duchy of Lithuania, and by 1503 he had tripled the territory of Muscovy, adopting the title of tsar and claiming the title of "Ruler of all Rus'". By his marriage to the niece of the last Byzantine emperor, he established Muscovy as the successor state of the Roman Empire, the "Third Rome".
Ivan's successor Vasili III also enjoyed military success, gaining Smolensk from Lithuania in 1512, pushing Muscovy's borders to the Dniepr River. Vasili's son Ivan IV (later known as Ivan the Terrible) was an infant at his father's death in 1533. He was crowned in 1547, assuming the title of tsar together with the proclamation of Tsardom of Russia (Russian: Царство Русcкое, Tsarstvo Russkoe).