The Cyrillic I is a letter used in almost all Cyrillic alphabets with the exception of Belarusian.

The Early Cyrillic alphabet, also called classical Cyrillic or paleo-Cyrillic, is an alphabetic writing system that was developed in Medieval Bulgaria in the Preslav Literary School during the late 9th century. It is used to write the Church Slavonic language, and was historically used for its ancestor, Old Church Slavonic. It was also used for other languages, but between the 18th and 20th centuries was mostly replaced by the modern Cyrillic script, which is used for some Slavic languages, and for East European and Asian languages that have experienced a great amount of Russian cultural influence.