Tsar of Bulgaria in the context of "Knyaz"

The Tsardom of Bulgaria (Bulgarian: Царство България, romanized: Tsarstvo Bŭlgariya), also known as the Third Bulgarian Tsardom (Bulgarian: Трето Българско Царство, romanized: Treto Bŭlgarsko Tsarstvo), usually known in English as the Kingdom of Bulgaria, or simply Bulgaria, was a constitutional monarchy in Southeastern Europe, which was established on 5 October [O.S. 22 September] 1908, when the Bulgarian state was raised from a principality to a tsardom.

Prince Ferdinand, founder of the royal family, was crowned as tsar at the Declaration of Independence, mainly because of his military plans and for seeking options for unification of all lands in the Balkans region with an ethnic Bulgarian majority (lands that had been seized from Bulgaria and given to the Ottoman Empire in the Treaty of Berlin). He and his successors were reckoned as kings internationally.

Tsar (/zɑːr, (t)sɑːr/; also spelled czar, tzar, or csar; Bulgarian: цар, romanized: tsar; Russian: царь, romanized: tsar'; Serbian: цар, car) is a title historically used by Slavic monarchs. The term is derived from the Latin word caesar, which was intended to mean emperor in the European medieval sense of the term—a ruler with the same rank as a Roman emperor, holding it by the approval of another emperor or a supreme ecclesiastical official—but was usually considered by Western Europeans to be equivalent to "king".

Tsar and its variants were the official titles in the First Bulgarian Empire (681–1018), Second Bulgarian Empire (1185–1396), the Kingdom of Bulgaria (1908–1946), the Serbian Empire (1346–1371), and the Tsardom of Russia (1547–1721).The first ruler to adopt the title tsar was Simeon I of Bulgaria. Simeon II, the last tsar of Bulgaria, is the last person to have held this title.

Ferdinand I (Ferdinand Maximilian Karl Leopold Maria; 26 February 1861 – 10 September 1948) was Prince of Bulgaria from 1887 to 1908 and Tsar of Bulgaria from 1908 until his abdication in 1918. Under his rule, Bulgaria entered the First World War on the side of the Central Powers in 1915.

Michael Asen III (Bulgarian: Михаил Асен III, romanized: Mihail Asen III), commonly known as Michael Shishman (Bulgarian: Михаил Шишман, romanized: Mihail Shishman), ruled as tsar of Bulgaria from 1323 to 1330. The exact year of his birth is unknown but it was between 1280 and 1292. He was the founder of the last ruling dynasty of the Second Bulgarian Empire, the Shishman dynasty. After he was crowned, however, Michael used the name Asen to emphasize his connection with the Asen dynasty, the first one to rule over the Second Empire.

An energetic and ambitious ruler, Michael Shishman led an aggressive but opportunistic and inconsistent foreign policy against the Byzantine Empire and the Kingdom of Serbia, which ended in the disastrous Battle of Velbazhd that claimed his own life. He was the last medieval Bulgarian ruler who aimed at military and political hegemony of the Bulgarian Empire over the Balkans and the last one who attempted to seize Constantinople. He was succeeded by his son Ivan Stephen and later by his nephew Ivan Alexander, who reversed Michael Shishman's policy by forming an alliance with Serbia.

The National Movement for Stability and Progress (Bulgarian: Национално движение за стабилност и възход, romanized: Natsionalno dvizhenie za stabilnost i vazhod, NDSV) is a liberal, populist political party in Bulgaria. It was known as the National Movement Simeon II (Bulgarian: Национално движение „Симеон Втори“, romanized: Natsionalno dvizhenie "Simeon Vtori") until 3 June 2007.

The party was created as a personal vehicle of Simeon of Saxe-Coburg-Gotha (Simeon II), the last Bulgarian Tsar (albeit nominally), who was deposed following the 1944 Bulgarian coup d'état, for his successful bid to become Prime Minister of Bulgaria in 2001. Simeon served as prime minister until 2005 and the party remained part of the governing coalition until 2009, when they lost all their seats in the National Assembly.