The Cyrillic alphabet or azbuka is an alphabetic writing system developed in the First Bulgarian Empire during the 10th century AD at the Preslav Literary School. It is used in various languages, past and present, of Eastern Europe and Asia, especially those of Slavic origin, and also non-Slavic languages influenced by Russian.

The alphabet is derived from the Ancient Greek uncial script, augmented by ligatures and consonants from the older Glagolitic alphabet for sounds not found in Ancient Greek. It is named in honor of the two Byzantine Greek brothers, Saints Cyril and Methodius, who created the Glagolitic alphabet earlier on. Modern scholars consider that Cyrillic was developed and formalized by early disciples of Cyril and Methodius (such as Clement of Ohrid).

With the accession of Bulgaria to the European Union on 1 January 2007, Cyrillic became the third official alphabet of the European Union, following the Latin and Greek alphabets.