For centuries, the southeastern shores of the Baltic Sea were inhabited by various Baltic tribes. In the 1230s, the Lithuanian lands were united by Mindaugas, the King of Lithuania, and the first unified Lithuanian state, the Kingdom of Lithuania, was created on 6 July 1253. During the 14th century, the Grand Duchy of Lithuania was the largest country in Europe; present-day Lithuania, Belarus, Ukraine, and parts of Poland and Russia were the territories of the Grand Duchy. With the Lublin Union of 1569, Lithuania and Poland formed a voluntary two-state union, the Polish–Lithuanian Commonwealth. The Commonwealth lasted more than two centuries, until neighbouring countries systematically dismantled it from 1772 to 1795, with the Russian Empire annexing most of Lithuania's territory.
The first known record of the name of Lithuania (Lithuanian: Lietuva) is in a 9 March 1009 story of Saint Bruno in the Quedlinburg Chronicle. The Chronicle recorded a Latinized form of the name Lietuva: Litua (pronounced [litua]). Due to the lack of reliable evidence, the true meaning of the name is unknown. Nowadays, scholars still debate the meaning of the word and there are a few plausible versions.
Since the word Lietuva has a suffix (-uva), the original word should have no suffix. A likely candidate is Lietā. Because many Balticethnonyms originated from hydronyms, linguists have searched for its origin among local hydronyms. Usually such names evolved through the following process: hydronym → toponym → ethnonym.Lietava, a small river not far from Kernavė, the core area of the early Lithuanian state and a possible first capital of the eventual Grand Duchy of Lithuania, is usually credited as the source of the name. However, the river is very small and some find it improbable that such a small and local object could have lent its name to an entire nation. On the other hand, such a naming is not unprecedented in world history.
Artūras Dubonis' proposed another hypothesis, that Lietuva relates to the word *leičiai (plural of leitis). From the middle of the 13th century, leičiai were a distinct warrior social group of the Lithuanian society subordinate to the Lithuanian ruler or the state itself. The word leičiai is used in the 14–16th-century historical sources as an ethnonym for Lithuanians (but not Samogitians) and is still used, usually poetically or in historical contexts, in the Latvian language, which is closely related to Lithuanian.