Why was Catherine the Great given this title?

Catherine the Great was a German princess. She married Prince Carl Peter Ulrich, the heir to the Russian throne. Being a bright personality with a strong sense of determination, she joined the Russian Orthodox Church, learned the Russian language, and by doing a lot of reading, acquired a brilliant education.

In June 1762, Catherine took an active part in a coup against her husband Emperor Peter III. He was overthrown, and soon killed ‘in an accident’, while Catherine became Russia’s autocratic ruler. Throughout her long reign, many reforms were undertaken, and the territory of Russia was further extended by acquiring the lands of Southern Ukraine and the Crimea. She promoted westernization and modernization as well as education. She was one of the greatest of Russian rulers, and hence her title, Catherine the Great. During her reign, Catherine continued the reforms begun by Peter the Great that ultimately led to the emergence of Russia onto the worldwide stage of politics.