A tsar (also spelled czar) was the title of the Russian emperors who ruled Russia for centuries. The word comes from Caesar, the title of Roman emperors, showing how Russian rulers saw themselves as heirs to ancient imperial power.

The most famous tsars include Peter the Great, who modernized Russia in the early 1700s by building a new capital city and creating a powerful navy, and Catherine the Great, who expanded Russian territory and supported arts and education. The last tsar, Nicholas II, ruled until 1917, when revolution swept through Russia and ended the tsarist system.

Tsars had absolute power over their vast empire, controlling everything from laws to military campaigns. They lived in magnificent palaces like the Winter Palace in St. Petersburg, while most Russian people remained poor farmers. This enormous gap between the ruler's wealth and the people's poverty contributed to growing unrest that eventually led to revolution.

Today, Americans sometimes use czar informally to describe someone appointed to take charge of a specific problem or program, like an “energy czar” or “drug czar.” These modern czars don't have royal power, but the term suggests they have broad authority to tackle a particular challenge.