The First Bulgarian Empire was a medieval Bulgarian state founded in AD 632 in the lands near the Danube Delta and disintegrated in AD 1018 after its annexation to the Byzantine Empire. At the height of its power it spread between Budapest and the Black Sea and from the Dnieper river in modern Ukraine to the Adriatic. It was succeeded by the Second Bulgarian Empire, established in 1185. The official name of the country since its very foundation was Bulgaria.

The Empire played a major role in European politics and was one of the strongest military powers of its time. In 717–718 the coalition of Byzantines and Bulgarians decisively defeated the Arabs in the siege of Constantinople thus saving Eastern Europe from the threat of an Arab invasion and Muslim conquest of Europe, and later destroyed the Avar Khanate expanding its territory to the Pannonian Plain and the Tatra Mountains. Bulgaria served as an effective shield against the constant invasions of nomadic peoples from the east in the so called second wave of the Great Migration. Pechenegs and Cumans were stopped in north-eastern Bulgaria and after a decisive victory over the Magyars in 896 they were forced to retreate to and permanently settle down in Pannonia.

To the south in course of the Byzantine–Bulgarian Wars the Bulgarians incorporated most of Slavic-populated region of Thrace and Macedonia. After the annihilation of the Byzantine army in the battle of Anchialus in 917 the Byzantine Empire was on the edge of destruction.

The Bulgars brought new construction and battle techniques to Europe. The first Bulgarian cities were made of large monolith stones unlike the Roman brick-build fortresses. With an area of 27 km² the capital Pliska was among the largest towns in Europe. The Inner town had a sewerage and floor heating long before cities such as Paris and London. After the adoption of Christianity in 864 Bulgaria became the cultural center of Slavic Europe. Its leading cultural position was further consolidated with the invention of the Cyrillic alphabet in Preslav, which some credit to the Bulgarian scholar Clement of Ohrid. According to some historians the schools of Preslav and Ohrid were the second universities in Europe after the University of Constantinople.