Princes and kings of the Balkan countries since 1800
Countries are covered in order of the establishment of the throne.

Ottoman Sultans

Selim III

1789-1807

Of the house of Osman, ruling since 1300; deposed by janissaries and later killed

Mustafa IV

1807-08

Cousin of Selim III; deposed and killed by a rebellion

Mahmud II

1808-39

Brother of Mustafa IV

Abdülmecid I

1839-61

Young son of Mahmud II

Abdülaziz

1861-76

Another son of Mahmud II; deposed and probably murdered

Murad V

1876

Son of Abdülmecid I; deposed as insane

Abdülhamid II

1876-1909

Another son of Abdülmecid I; deposed by vote of parliament

Mehmed V Reşad

1909-18

Another son of Abdülmecid I

Mehmed VI Vahdeddin

1918-22

Another son of Abdülmecid I; sultanate abolished in 1922

Rulers of Montenegro

Peter I

1782-1830

Prince-
  Bishop

Of the Petrović-Njegoš dynasty of prince-bishops, ruling since 1696

Peter II

1830-51

Prince-
  Bishop

Nephew of Peter I

Danilo

1851-52
 
1852-60

Prince-
  Bishop
Prince

Cousin of Peter II; assassinated

Nicholas

1860-1910
1910-18

Prince
King

Nephew of Danilo; deposed in preparation for Montenegro's absorption into Yugoslavia

Rulers of Serbia/Yugoslavia
K = Karadjordjević line     O = Obrenović line

Djordje Petrović (Karadjordje)

1804-13

Lord

First ruler, went into exile after defeat by Ottomans; killed in 1817 by order of his successor

Miloš Obrenović

1817-39

Prince

Hereditary prince from 1830; abdicated in protest against a Russian-imposed constitution

Milan (O)

1839

Prince

Son of Miloš

Michael (O)

1839-42

Prince

Another son of Miloš; fled the country

Alexander (K)

1842-58

Prince

Son of Karadjordje; brought to the throne by vote of the notables; forced to abdicate

Miloš Obrenović (again)

1858-60

Prince

Forced to abdicate

Michael (O, again)

1860-68

Prince

Assassinated

Milan II (O)

1868-82
1882-89

Prince
King

Cousin of Michael; abdicated in protest against a liberalized constitution

Alexander I (O)

1889-1903

King

Son of Milan II; assassinated

Peter I (K)

1903-21

King

Son of Prince Alexander (1842-58); elected to the throne by the Skupština; declared insane in 1914, with his son Alexander as Regent

Alexander II (K)

1921-34

King

Son of Peter I; assassinated

Peter II (K)

1934-45

King

Young son of Alexander II, with Prince Paul as Regent until 1941; in exile during the war; never returned, as Yugoslavia became a republic in 1945

Kings of Greece

Otto I

1833-62

First ruler, a Bavarian prince chosen by the protecting Powers; deposed

George I

1863-1913

A Danish prince chosen by the protecting Powers; assassinated

Constantine I

1913-17

Son of George I; abdicated under Allied pressure

Alexander

1917-20

A younger son of Constantine I, imposed by Allied pressure; deposed by plebiscite

Constantine I (again)

1920-22

Restored by plebiscite, despite Allied pressure; abdicated under pressure; d. 1923

George II

1922-23
1935-47

Eldest son of Constantine I; from 1923 to 1935 Greece was a republic

Paul

1947-64

Yet another son of Constantine I

Constantine II

1964-73

Son of Paul; in exile after 1967, deposed in 1973 to create a republic

Rulers of Romania

Alexander John Cuza

1859-66

Prince

A native boyar, elected prince of both Wallachia and Moldavia, separately, so as to informally create a united country; forced to abdicate

Carol I

1866-81
1881-1914

Prince
King

First ruler of an officially united Romania; a Hohenzollern-Sigmaringen princeling

Ferdinand

1914-27

King

Nephew of Carol I

Michael

1927-30

King

Grandson of Ferdinand; elevated (as a child) in place of his discredited father Carol, with a regency

Carol II

1930-40

King

Son of Ferdinand, father of Michael; maneuvered his way back onto the throne; eventually fled the country

Michael (again)

1940-47

King

Abdicated under pressure and a republic was established

Rulers of Bulgaria

Alexander

1879-86

Prince

First ruler, a Battenberg princeling; abdicated under Russian pressure

Ferdinand

1887-1908
1908-18

Prince
Tsar

A Saxe-Coburg princeling; abdicated upon Bulgaria's defeat in WWI

Boris III

1918-43

Tsar

Son of Ferdinand

Simeon II

1943-46

Tsar

Young son of Boris, ruled under a regency; in 1946 a republic was declared by plebiscite

Kings of Albania

William (of Wied)

1914

First ruler, a German princeling who accepted the new crown in Feb. but fled in Sept after the war began; when Albania reemerged after the war, it chose to be a republic

Zog

1928-39

President who had himself made king; reign ended with Albania's incorporation into Italy