| Country | Sovereign | Born | Acceded | Consort (born) | Heir (born) |
 Principality of Liechtenstein |  Prince Johann II | 5 Oct 1840 | 12 Nov 1858 |  Prince Franz (1853) | |
 Kingdom of Spain |  King Alfonso XIII | 17 May 1886 | 17 May 1886 |  Queen Victoria Eugenie (1887) |  Infante Alfonso, Prince of Asturias (1907) |
 Kingdom of the Netherlands |
 Queen Wilhelmina | 31 Aug 1880 | 23 Nov 1890 |  Prince Hendrik (1876) |  Princess Juliana (1909) |
 Kingdom of Italy |  King Victor Emanuel III | 11 Nov 1869 | 29 Jul 1900 |  Queen Helena (1873) |  Crown Prince Umberto (1904) |
 Kingdom of Norway |  King Haakon VII | 3 Aug 1872 | 18 Nov 1905 |  Queen Maud (1869) |  Crown Prince Olav (1903) |
 Kingdom of Sweden |  King Gustaf V | 16 Jun 1858 | 8 Dec 1907 |  Queen Victoria (1862) |  Crown Prince Gustaf Adolf (1882) |
 Kingdom of Belgium |  King Albert I | 8 Apr 1875 | 23 Dec 1909 |  Queen Elisabeth (1876) |  Prince Leopold, Duke of Brabant (1901) |
 United Kingdom of Great Britain and Ireland Irish Free State |  King George V | 3 Jun 1865 | 6 May 1910 |  Queen Mary (1867) |  Prince Edward, Prince of Wales (1894) |
 Kingdom of Denmark  Kingdom of Iceland (1 Dec 1918) |  King Christian X | 26 Sep 1870 | 14 May 1912 |  Queen Alexandrine (1879) |  Crown Prince Frederik (1899) |
 Kingdom of Romania |  King Ferdinand I | 24 Aug 1865 | 10 Oct 1914 |  Queen Marie (1875) |  Crown Prince Carol (1893) |
 Kingdom of Bulgaria |  King Boris III | 30 Jan 1894 | 3 Oct 1918 |  Kyril, Prince of Preslav (1895) | |
 Grand Duchy of Luxembourg |  Grand Duchess Charlotte | 23 Jan 1896 | 14 Jan 1919 |  Prince Felix (1893) | Her. Grand Duke Jean (1921) |
 Kingdom of Hungary (29 Feb 1920) | (Admiral Miklós Horthy, Regent) | (18 Jun 1868) | (1 Mar 1920) | ||
 Kingdom of Serbs, Croats, & Slovenes (1 Dec 1918) |  King Alexander I | 16 Dec 1888 | 16 Aug 1921 |  Queen Marie (1900) |  Crown Prince Peter (1923) |
 Principality of Monaco |  Prince Louis II | 12 Jul 1870 | 26 Jun 1922 |  Princess Charlotte (1898) | |
 Kingdom of Greece |  King George II | 19 Jul 1890 | 27 Sept 1922 |  Queen Elisabeth (1894) |  Crown Prince Paul (1901) |