The Kingdom of Croatia (Croatian: Kraljevina Hrvatska; Latin: Regnum Croatiae; Hungarian: Horvát Királyság, German: Königreich Kroatien) was part of the Lands of the Hungarian Crown, but was subject to direct Imperial Austrian rule for significant periods of time, including its final years.

The territory of the Slavonian kingdom was recovered from the Ottoman Empire, and was subsequently part of the Military Frontier for a short period.

Following the fall of the medieval Kingdom of Hungary at the Battle of Mohács, in 1527 the Croatian and Hungarian nobles needed to decide on a new king.

This siege, now known as the Battle of Szigetvár, bought enough time to allow Austrian troops to regroup before the Ottomans could reach Vienna.

Due to the dangerous proximity to the Ottoman armies, the area became rather deserted, so Austria encouraged the settlement of Serbs, Germans, Hungarians, Czechs, Slovaks and Rusyns/Ukrainians and other Slavs in the Military Frontier, creating an ethnic patchwork.

Matija Gubec and other leaders of the mutiny raised peasants to arms in over sixty fiefs throughout the country in January 1573, but their uprising was crushed by early February.

Subsequently, the empress made significant contributions to Croatian matters, by making several reforms in the administrative control of the Military Frontier, the feudal and tax system.

With the fall of the Venetian Republic in 1797, its possessions in the eastern Adriatic mostly came under the authority of France which passed its rights to Austria the same year.

The movement attracted a number of influential figures and produced some important advances in the Croatian language and culture.

Despite this contribution, Croatia was later subject to Baron Alexander von Bach's absolutism as well as Hungarian hegemony under Ban Levin Rauch when the Austrian Empire was transformed into a dual monarchy of Austria-Hungary in 1867.

After the fall of Bach's absolutism (the October Diploma of 1860 and the February Patent of 1861), the Royal Croatian-Slavonian Court Chancellery (Croatian: Kraljevska hrvatsko-slavonska dvorska kancelarija) in Vienna - from 1861 to 1862 "courtly (aulic) department for Croatia and Slavonia" (ministry) - and the Croatian-Slavonian-Dalmatian Royal Council of Lieutenancy (also known as the Croatian-Slavonian-Dalmatian Vice-regency Council, it was headed by the ban; Croatian: Kraljevsko namjesničko vijeće) in Zagreb were founded.

[9] Ban Jelačić had succeeded in the abolition of serfdom in Croatia, which eventually brought about massive changes in society: the power of the major landowners was reduced and arable land became increasingly subdivided, to the extent of risking famine.

It would eventually develop into two major causes: The loss of Croatian domestic autonomy was rectified a year after the Austro-Hungarian Compromise of 1867, when in 1868 the Croatian–Hungarian Settlement was negotiated, which combined Croatia and Slavonia into the autonomous Kingdom of Croatia-Slavonia.

The Kingdom of Croatia was divided into counties (Croatian: županije; German: Comitate (modern spelling Komitate) or Gespanschaften; Hungarian: vármegyék; Latin (also in other languages): comitatus).

In the late 18th century a fourth – Severin County – existed, carved out of the part of Zagreb County west of the Kupa, but it lasted for less than a decade before being reintegrated; however, the coastal area was instead attached to the Corpus separatum of Fiume (Rijeka) as the Hungarian or Croatian Littoral.

[14] In 1850 the counties were formally referred to in German as Gespanschaften and were divided into political districts akin to those of modern Austria,[13] much like most of the rest of the Empire.

According to the 1802 data, the population of the Kingdom of Croatia included 400,000 (98.8%) Roman Catholics, 4,800 (1.2%) Eastern Orthodox Christians and 40 Protestants.

According to the data he collected and processed, 526,550 people lived in the Kingdom of Croatia, out of which 519,426 (98.64%) were Croats, 3,000 (0.56%) Germans, 2,900 (0.55%) Serbs and 1,037 (0.19%) Jews.

The new flag was the Croatian tricolor of red, white, and blue, and it was to remain the symbol of Croatia up to the present day.