The Grand Duchy of Lithuania was a sovereign state in northeastern Europe that existed from the 13th century, succeeding the Kingdom of Lithuania, to the late 18th century, when the territory was suppressed during the 1795 partitions of Poland–Lithuania. The state was founded by Lithuanians, who were at the time a polytheistic nation of several united Baltic tribes from Aukštaitija. By 1440 the grand duchy had become the largest European state, controlling an area from the Baltic Sea in the north to the Black Sea in the south.
The grand duchy expanded to include large portions of the former Kievan Rus' and other neighbouring states, including what is now Lithuania, Belarus, most of Ukraine as well as parts of Latvia, Poland, Moldova and Russia. It was a multi-ethnic and multiconfessional state, with great diversity in languages, religion, and cultural heritage.
The consolidation of the Lithuanian lands began in the late 13th century. Mindaugas, the first ruler of the grand duchy, was crowned as the Catholic King of Lithuania in 1253. The pagan state was targeted in a religious crusade by the Teutonic Knights and the Livonian Order, but survived. Its rapid territorial expansion started late in the reign of Gediminas, and continued under the co-leadership of his sons, Algirdas and Kęstutis. Algirdas's son Jogaila signed the Union of Krewo in 1386, bringing two major changes in the history of the Grand Duchy of Lithuania: the conversion to Christianity of Europe's last pagan state, and the establishment of a dynastic union between the Grand Duchy of Lithuania and the Crown of the Kingdom of Poland. This marked the beginning of the rule of other countries by the patrilineal members of the Lithuanian ruling Gediminid dynasty, who since the 14th–15th centuries ruled not only Lithuania, but also Poland, Hungary, Croatia, Bohemia, and Moldavia.
The reign of Vytautas the Great, son of Kęstutis, marked both the greatest territorial expansion of the grand duchy and the defeat of the Teutonic Knights in the Battle of Grunwald in 1410. It also marked the rise of the Lithuanian nobility. After Vytautas's death, Lithuania's relationship with the Kingdom of Poland greatly deteriorated. Lithuanian noblemen, including the Radvila family, attempted to break the personal union with Poland. However, unsuccessful wars with the Grand Duchy of Moscow forced the union to remain intact.
Eventually, the Union of Lublin of 1569 created a new state, the Polish–Lithuanian Commonwealth. In this federation, the Grand Duchy of Lithuania maintained its political distinctiveness and had separate ministries, laws, army, and treasury. The federation was terminated by the passing of the Constitution of 3 May 1791, when it was supposed to become a single country, the Commonwealth, under one monarch and parliament, and with no Lithuanian autonomy. Shortly afterward, the unitary character of the state was confirmed by adopting the Reciprocal Guarantee of Two Nations. However, the newly reformed Commonwealth was invaded by Russia in 1792 and partitioned between neighbouring states. A truncated state (whose principal cities were Kraków, Warsaw and Vilnius) remained that was nominally independent. After the Kościuszko Uprising, the territory was completely partitioned among the Russian Empire, the Kingdom of Prussia and Austria in 1795.
The name of Lithuania (Litua) was first mentioned in 1009 in Annals of Quedlinburg. Some older etymological theories relate the name to a small river not far from Kernavė, the core area of the early Lithuanian state and a possible first capital of the would-be Grand Duchy of Lithuania, is usually credited as the source of the name. This river's original name is Lietava. As time passed, the suffix -ava could have changed into -uva, as the two are from the same suffix branch. The river flows in the lowlands and easily spills over its banks, therefore the traditional Lithuanian form liet- could be directly translated as lietis (to spill), of the root derived from the Proto-Indo-European leyǝ-. 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 fact is not unprecedented in world history. A credible modern theory of etymology of the name of Lithuania (Lithuanian: Lietuva) is Artūras Dubonis's hypothesis that Lietuva relates to the word leičiai (plural of leitis, a social group of warriors-knights in the early Grand Duchy of Lithuania). The title of the Grand Duchy was consistently applied to Lithuania from the 14th century onward.
Naming convention of both title of ruler (hospodar) and the state changed as it expanded its territory. Following the decline of the Kingdom of Ruthenia and incorporation of its lands into the Grand Duchy of Lithuania, Gediminas started to title himself as "King of Lithuanians and many Ruthenians", while the name of the state became the Grand Duchy of Lithuania and Ruthenia. Similarly the title changed to "King of Lithuanians and Ruthenians, ruler and duke of Semigallia" when Semigallia became part of the state. The 1529 edition of the Statute of Lithuania described the titles of Sigismund I the Old as "King of Poland, the Grand Duke of Lithuania, Ruthenia, Prussia, Samogitia, Mazovia, and other [lands]". However, in the final Third Statute of Lithuania (adopted in 1588) the country's name was written only as the "Grand Duchy of Lithuania".
The country was also referred to as the Republic of Lithuania (Latin: Respublica Lituana) since at least the mid-16th century, even before the Union of Lublin in 1569.
The first mention of the name Lithuania is found in the Annals of Quedlinburg, which describes the missionary expedition of Bruno of Querfurt to Yotvingians. In the 12th century, Slavic chronicles refer to Lithuania as one of the areas attacked by the Rus'. Pagan Lithuanians initially paid tribute to Polotsk, but they soon grew in strength and organized their own small-scale raids. At some point between 1180 and 1183 the situation began to change, and the Lithuanians started to organize sustainable military raids on the Slavic provinces, raiding the Principality of Polotsk as well as Pskov, and even threatening Novgorod. The sudden spark of military raids marked consolidation of the Lithuanian lands in Aukštaitija. The Lithuanians are the only branch within the Baltic group that managed to create a state entity in premodern times.
The Lithuanian Crusade began after the Livonian Order and Teutonic Knights, crusading military orders, were established in Riga and in Prussia in 1202 and 1226 respectively. The Christian orders posed a significant threat to pagan Baltic tribes, and further galvanized the formation of the Lithuanian state. The peace treaty with Galicia–Volhynia of 1219 provides evidence of cooperation between Lithuanians and Samogitians. This treaty lists 21 Lithuanian dukes, including five senior Lithuanian dukes from Aukštaitija (Živinbudas, Daujotas, Vilikaila, Dausprungas and Mindaugas) and several dukes from Žemaitija. Although they had battled in the past, the Lithuanians and the Žemaičiai now faced a common enemy. Likely Živinbudas had the most authority and at least several dukes were from the same families. The formal acknowledgement of common interests and the establishment of a hierarchy among the signatories of the treaty foreshadowed the emergence of the state.
Mindaugas, the duke of southern Lithuania, was among the five senior dukes mentioned in the treaty with Galicia–Volhynia. The Livonian Rhymed Chronicle, reports that by the mid-1230s, Mindaugas had acquired supreme power in the whole of Lithuania. In 1236, the Samogitians, led by Vykintas, defeated the Livonian Order in the Battle of Saule. The Order was forced to become a branch of the Teutonic Knights in Prussia, making Samogitia, a strip of land that separated Livonia from Prussia, the main target of both orders. The battle provided a break in the wars with the Knights, and Lithuania exploited this situation, arranging attacks on the Ruthenian provinces and annexing Navahrudak and Hrodna.