Tsar is a title for the supreme ruler in several countries.
In Bulgaria, the title was used in 913–1422 and again in 1908–1946. The last tsar to rule Bulgaria was Boris III, who replaced Ferdinand I of Bulgaria 1918.
In Serbia, the title was used in 1346—1371. The last tsar to rule Serbia was Stephen Uroš V.
In the Russian Empire, the title was used from 1546 until 1721. Starting in 1721, the title of Russian emperors was imperator, but the word tsar remained in common use until the Russian Revolution in 1917. The last tsar to rule Russia was Nicholas II, who replaced Alexander III in 1894. The system of government used during the Tsardom of Russia and the Russian Empire was called Tsarist autocracy, also known as Tsarism.
Tsar is also spelled tzar, czar, and csar. It is the Eastern European word for caesar. It can be translated to emperor.