The
monarchs of Bulgaria ruled the country, with interruptions, from the establishment of the
First Bulgarian Empire in 681 to the abolition of monarchy in a manipulated
referendum held on 15 September 1946. The Bulgarian monarchy had two periods of foreign domination: one century and a half of Byzantine rule and almost five centuries of Ottoman rule. Early Bulgarian rulers possibly used the title
khan, later
knyaz for a brief period, and subsequently
tsar.