Alexander I, also known as Alexander the Unifier, was King of the Serbs, Croats and Slovenes from 16 August 1921 to 3 October 1929 and King of Yugoslavia from 3 October 1929 until his assassination in 1934. His reign of 13 years is the longest of the three monarchs of the Kingdom of Yugoslavia.

The May Coup was a coup d'état which resulted in the assassination of King Alexander I of Serbia and his consort, Queen Draga, inside the Royal Palace 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 the Kingdom of Serbia since the middle of the 19th century. A group of Royal Serbian Army officers led by Captain Dragutin Dimitrijević (Apis) organized the assassination. After the May Coup, the throne passed to King Peter I of Serbia.