The subdivisions of the Kingdom of Yugoslavia (initially known as the Kingdom of Serbs, Croats, and Slovenes) existed successively in three different forms. From 1918 to 1922, the kingdom maintained the pre-World War I subdivisions of Yugoslavia's predecessor states. In 1922, the state was divided into 33 oblasts or provinces and, in 1929, a new system of nine banates (in Serbo-Croatian, the word for "banate" is banovina) was implemented.
From 1918 to 1922, Kingdom of Serbs, Croats, and Slovenes continued to be subdivided into the pre-World War I divisions of Austria-Hungary and the formerly independent kingdoms of Serbia and Montenegro.
Provinces (pokrajine) were:
These were subdivided into districts and counties:
The Vidovdan Constitution of 1921 established the Kingdom of Serbs, Croats, and Slovenes as a unitary state and, in 1922, 33 new administrative oblasts (counties) ruled from the centre were instituted. These bore no relation to the earlier divisions and, in the interest of promoting Yugoslavism, statism and multiculturalism, were not given any ethnic or national names. They were largely named after rivers, regions and cities from which they were administrated. They were unpopular in parts of the country since their formation, which led to the creation of banates.
From 1929, the kingdom was subdivided into nine new provinces or banates called banovinas. Their borders were intentionally drawn so that they would not correspond either to boundaries between ethnic groups, or to pre-World War I imperial borders. Except for the Littoral Banovina, they were named after major rivers. Slight changes to their borders were made in 1931 with the new Yugoslav Constitution. The banates (banovinas) were as follows:
The City of Belgrade, together with Zemun and Pančevo was also an administrative unit independent of the surrounding Danube Banovina.
As an accommodation to Croatian politicians in the Cvetković-Maček Agreement, the Banovina of Croatia (Banovina Hrvatska) was formed in 1939 from a merger of the Littoral and Sava Banovinas, with some additional territory from the Drina, Dunav, Vrbas and Zeta Banovinas where ethnic Croats formed the majority of the population. Like Sava, its capital was Zagreb, the second largest city in the country.