Lithuanian is a representative of the Baltic group of the Indo-European languages. Currently, only Latvian is closely related to it. Prussian, a member of the same family, disappeared along with the Prussian community, which had inhabited its own territory, the present day Kaliningrad Region, which was conquered by the Teutonic Orders during the Middle Ages and subsequently germanised.

The four ethnic groups of Lithuanians have preserved their dialects, which differ in their phonetic, morphological and syntactic features, and even in vocabulary.

Standard Lithuanian was formed on the basis of Latin vocabulary. This was a lengthy process, beginning in the 16th century. It was, during that period that the first Lithuanian books appeared in print. Due to historical causes and an unfavourable political destiny, the formation of a standard language continued for several centuries and was completed only during the first part of the 20th century. The Lithuanian alphabet contains 32 letters and there are six cases.

It is claimed at times that Lithuanian is descended from Sanskrit. This hypothesis finds a sizeable number of supporters.