Mindaugas was the first known grand duke of Lithuania and the only crowned king of Lithuania. Little is known of his origins, early life, or rise to power; he is mentioned in a 1219 treaty as an elder duke, and in 1236 as the leader of all the Lithuanians. The contemporary and modern sources discussing his ascent mention strategic marriages along with banishment or murder of his rivals. He extended his domain into regions southeast of Lithuania proper during the 1230s and 1240s. In 1250 or 1251, during the course of internal power struggles, he was baptised as a Roman Catholic; this action enabled him to establish an alliance with the Livonian Order, a long-standing antagonist of the Lithuanians. By 1245, Mindaugas was already being referred to as "the highest king" in certain documents. During the summer of 1253, he was crowned king, ruling between 300,000 and 400,000 subjects and got nicknamed as Mindaugas the Sapient by the Livonians.

Lithuanians are a Baltic ethnic group. They are native to Lithuania, where they number around 2,378,118 people. Another two millions make up the Lithuanian diaspora, largely found in countries such as the United States, United Kingdom, Brazil, Russia, and Canada. Their native language is Lithuanian, one of only two surviving members of the Baltic language family along with Latvian. According to the census conducted in 2021, 84.6% of the population of Lithuania identified themselves as Lithuanians, 6.5% as Poles, 5.0% as Russians, 1.0% as Belarusians, and 1.1% as members of other ethnic groups. Most Lithuanians belong to the Catholic Church, while the Lietuvininkai who lived in the northern part of East Prussia prior to World War II, were mostly Lutherans.