The Theme of Bulgaria (Greek: Θέμα Βουλγαρίας, romanized: Thema Boulgarias) was a theme (province) of the Byzantine Empire established by Emperor Basil II after the conquest of Bulgaria in 1018. Its capital was Skopje and it was governed by a strategos. The theme of Bulgaria did not encompass the old Bulgarian lands between the Haimos Mountains and the river Danube, that included the former capitals Pliska and Preslav. This territory was administered independently and was considered as autonomous military unit, designated as Paristrion or Paradunavon, meaning the "lands beside the Danube".
The local inhabitants were called Bulgarians, but some authors maintain this name did not have an ethnic meaning. Bulgaroi was a political name, in the same way as Romaioi. The emotive force which the name has today is quite distinct from that which inspired the emperors John I and Basil II to celebrate their victories with elaborate ceremony. Their achievement was to restore the empire to her ancient limits, and eliminate the rival, distinct, independent empire that had emerged from the Byzantine model and had been established and recognized within those limits. It can be seen from the fact that the rebels in the Uprising of 1072 invited a Serbian king from Diokleia Constantine Bodin, which belonged to the former empires of Simeon I of Bulgaria and Samuel of Bulgaria, to be the Tsar of the Bulgarians. However, some authors suggest that Bodin was invited, because he was the great-great-grandson of Samuel of Bulgaria.