The name Old Russian language has been applied to different things.

• Old East Slavic language was the language of Kievan Rus', spoken from the 9th to 14th centuries. It was the ancestor of the East Slavic languages Belarusian, Russian, Rusyn, and Ukrainian.
• For the language of Muscovite Russia in the 15th to 17th centuries, see the Muscovite section of History of the Russian language.