|Ruthenian literary language|
|руска(я) мова / ruska(ja) mova|
|Native to||East Slavic regions of the Polish–Lithuanian Commonwealth|
|Extinct||Developed into Belarusian, Ukrainian and Rusyn|
Ruthenian language (Latin: lingua ruthenica, also see other names) is a common exonymic designation for a group of East Slavic linguistic varieties, particularly those that were spoken from the 15th to 18th centuries in the East Slavic regions of the Grand Duchy of Lithuania and the Polish–Lithuanian Commonwealth. Regional distribution of those varieties, both in their literary and vernacular forms, corresponded (approximately) to territories of modern states of Belarus and Ukraine. By the end of the 18th century, they gradually diverged into regional variants, that subsequently developed into modern languages: Belarusian, Ukrainian and Rusyn.
In the former Austrian Empire, and also in the Austro-Hungarian Monarchy, the same term (German: Ruthenische sprache, Hungarian: Rutén nyelv) was employed continuously (up to 1918) as an official exonymic designation for the entire East Slavic linguistic body within the borders of the Monarchy.
Several linguistic issues, related to this language, are debated among scholars. Those issues include: various questions related to classification of literary and vernacular varieties of this language; issues related to meanings and proper uses of various endonymic (native) and exonymic (foreign) linguonyms (names of languages and linguistic varieties); questions on its relations to modern East Slavic languages, and its relations to the Old East Slavic, that was the colloquial language used in Kievan Rus' (10th–13th centuries).