The Bulgarian Cyrillic alphabet (Bulgarian: Българска кирилица) is used to write the Bulgarian language. The Cyrillic alphabet was originally developed in the First Bulgarian Empire during the 9th – 10th century AD at the Preslav Literary School.

It has been used in Bulgaria (with modifications and exclusion of certain archaic letters via spelling reforms) continuously since then, superseding the previously used Glagolitic alphabet, which was also invented and used there before the Cyrillic script overtook its use as a written script for the Bulgarian language. The Cyrillic alphabet was used in the then much bigger territory of Bulgaria (including most of today's Serbia), North Macedonia, Kosovo, Albania, Northern Greece (Macedonia region), Romania and Moldova, officially from 893. It was also transferred from Bulgaria and adopted by the East Slavic languages in Kievan Rus' and evolved into the Belarusian, Russian and Ukrainian alphabets and the alphabets of many other Slavic (and later non-Slavic) languages. Later, some Slavs modified it and added/excluded letters from it to better suit the needs of their own language varieties.