Alexander I of Serbia in the context of "Alexander I of Yugoslavia"

Milan Obrenović IV (Serbian Cyrillic: Милан Обреновић, romanized: Milan Obrenović; 22 August 1854 – 11 February 1901) reigned as the Prince of Serbia from 10 June 1868 until 1882, when he became King of Serbia, a title he held until his abdication on 6 March 1889. His son, Alexander I of Serbia, became the second King of Serbia.

The May Coup (Serbian: Мајски преврат, romanized: Majski prevrat) was a coup d'état in the Kingdom of Serbia which resulted in the assassination of King Alexander I and his consort, Queen Draga, inside the Stari Dvor in Belgrade on the night of 10–11 June [O.S. 28–29 May] 1903. This act resulted in the extinction of the Obrenović dynasty that had ruled Serbia since the middle of the 19th century. A group of army officers led by Captain Dragutin Dimitrijević (Apis) organized the assassination. After the May Coup, the throne passed to King Peter I of the Karađorđević dynasty.

Along with the royal couple, the conspirators killed prime minister Dimitrije Cincar-Marković, minister of the army Milovan Pavlović [sr], and general-adjutant Lazar Petrović. The coup had a significant influence on Serbia's relations with other European powers; the Obrenović dynasty had mostly allied with Austria-Hungary, while the Karađorđević dynasty had close ties both with Russia and with France. Each dynasty received ongoing financial support from their powerful foreign sponsors.

Draginja "Draga" Obrenović (Serbian Cyrillic: Драгиња "Драга" Обреновић; 23 September [O.S. 11 September] 1867 – 11 June [O.S. 29 May] 1903), née Lunjevica (Луњевица) and formerly Mašin (Машин), was Queen of Serbia as the wife of King Aleksandar Obrenović. She was formerly a lady-in-waiting to Aleksandar's mother, Queen Natalija (until 1897).

Dragutin Dimitrijević (Serbian Cyrillic: Драгутин Димитријевић; 17 August 1876 – 26 June 1917), better known by his nickname Apis (Апис), was a Serbian army officer and chief of the military intelligence section of the Royal Serbian Army general staff in 1913. He is best known as the main leader of the Black Hand, a paramilitary secret society devoted to South Slav irredentism that organised the 1903 overthrow of the Serbian government and assassination of King Alexander I of Serbia and Queen Draga. Many scholars believe that he also sanctioned and helped organize the conspiracy behind the assassination of Archduke Franz Ferdinand on 28 June 1914. This led directly to the July Crisis and the outbreak of World War I.

In 1916, the government in exile of Serbian Prime Minister Nikola Pašić, who considered Dimitrijević's refusal to compromise on South Slav irredentism to represent a serious threat to the secret peace negotiations taking place with Vienna during the Sixtus Affair, filed charges of high treason against the leadership of Unification or Death. Dimitrijević was tried in Thessaloniki before a Serbian Army court martial arraigned by his opponents within the Serbian government. He was found guilty of conspiring to assassinate both the Archduke and Prince Regent Alexander Karađorđević and executed by firing squad, along with two senior associates on 26 June 1917.

Persida Karađorđević née Nenadović (Serbian Cyrillic: Персида Ненадовић; 15 February 1813 – 29 March 1873) was the Princess of Serbia as the wife of Alexander Karađorđević, who ruled the Principality of Serbia from his election on 14 September 1842 until his abdication on 24 October 1858. She was the mother of ten children, including future king Peter I of Serbia, who succeeded to the throne after the assassination of King Alexander I, the last ruler of the Obrenović dynasty (the traditional rivals of the Karađorđevićs).