
Old Church Slavonic or Old Slavonic was the first Slavic literary language.

The Archbishopric of Moravia was an ecclesiastical province, established by the Holy See to promote Christian missions among the Slavic peoples. Its first archbishop, the Byzantine Methodius, persuaded Pope John VIII to sanction the use of Old Church Slavonic in liturgy. Methodius had been consecrated archbishop of Pannonia by Pope Adrian II at the request of Koceľ, the Slavic ruler of Pannonia in East Francia in 870.

Cyril and Methodius (815–885) were two brothers and Byzantine Christian theologians and missionaries. For their work evangelizing the Slavs, they are known as the "Apostles to the Slavs".

The Glagolitic script is the oldest known Slavic alphabet. It is generally agreed to have been created in the 9th century by Saint Cyril, a monk from Thessaloniki. He and his brother, Saint Methodius, were sent by the Byzantine Emperor Michael III in 863 to Great Moravia to spread Christianity among the West Slavs in the area. The brothers decided to translate liturgical books into the contemporary Slavic language understandable to the general population. As the words of that language could not be easily written by using either the Greek or Latin alphabets, Cyril decided to invent a new script, Glagolitic, which he based on the local dialect of the Slavic tribes from the Byzantine theme of Thessalonica.

Hilandar Fragments are a Serbian medieval manuscript from the end of the 10th and the beginning of the 11th century. It is one of the oldest preserved Slavic monuments written in Cyrillic script.

The Novgorod Codex is the oldest book of the Rus’, unearthed on July 13, 2000 in Novgorod. It is a palimpsest consisting of three bound wooden tablets containing four pages filled with wax, on which its former owner wrote down dozens, probably hundreds of texts during two or three decades, each time wiping out the preceding text.

Pokrytie is one of the historic diacritical signs of Cyrillic that was used in Old Church Slavonic, later medieval Cyrillic literary traditions and modern Church Slavonic.

The Temnić inscription is one of the oldest records of Old Church Slavonic Cyrillic script from the territory of modern Serbia, dated to the late 10th, or early 11th century, when this territory was part of the First Bulgarian Empire. The limestone plate was discovered in the vicinity of a school in the village of Gornji Katun, near Varvarin, in the region of Temnić in Pomoravlje. It was acquired by the National Museum of Serbia in 1909. The tablet represents a scientific conundrum as no other remains of an edifice were found and paleographic and linguistic analysis of the text reveals little information.