The town used to be called Rudo Polje, Karanovac or Rankovićevo (after Aleksandar Ranković). It bears its current name, which means "royal town", after the Serbian king Milan I (reigned 1868 to 1889), who raised Kraljevo to a diocese instead of Čačak. During the First World War the city was occupied by the Austrians.
In the course of the occupation of Yugoslavia during the Second World War, the German Wehrmacht moved into the city in 1941. In retaliation against Chetnik actions, they carried out the Kraljevo and Kragujevac massacres in October 1941, killing several thousand civilians. The massacre took place in front of and in a large assembly hall, which was then brought to Wiener Neustadt in more than 400 freight cars and rebuilt there, which is why the hall was popularly known as the "Serb Hall".
Source: Wikipedia