Lithuanians (lietuviai) 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.
The territory of the Balts, including modern Lithuania, was once inhabited by several Baltic tribal entities (Aukštaitians, Sudovians, Old Lithuanians, Curonians, Semigallians, Selonians, Samogitians, Skalvians, Old Prussians (Nadruvians)), as attested by ancient sources and dating from prehistoric times. Over the centuries, and especially under the Grand Duchy of Lithuania, some of these tribes consolidated into the Lithuanian nation, mainly as a defence against the marauding Teutonic Order and Eastern Slavs. The Lithuanian state was formed in the High Middle Ages, with different historians dating this variously between the 11th and mid-13th centuries. Mindaugas, Lithuania's only crowned king and its first baptised ruler, is generally considered Lithuania's founder. The Lithuanians are the only branch of Baltic people that managed to create a state entity before the modern era. During the Late Middle Ages, Lithuania was ravaged by the Lithuanian Crusade, which ended only by the Treaty of Melno in 1422. In fact, the crusade persisted after the definite Christianization of Lithuania in 1387, when Europe's last pagan people were baptised. Simultaneously, the Lithuanian state reached its apogee under the rule of Vytautas the Great (1392–1430), when it ruled the lands between the Baltic and Black seas.