Croatia proper in the context of "Primorje-Gorski Kotar County"

Stephen Tvrtko I (Serbo-Croatian: Stjepan/Stefan Tvrtko / Стјепан/Стефан Твртко; c. 1338 – 10 March 1391) was the first king of Bosnia. A member of the House of Kotromanić, he succeeded his uncle Stephen II as the ban of Bosnia in 1353. As he was a minor at the time, Tvrtko's father, Vladislav, briefly ruled as regent, followed by Tvrtko's mother, Jelena. Early in his personal rule, Tvrtko quarrelled with his country's Roman Catholic clergy but later enjoyed cordial relations with all the religious communities in his realm. After initial difficulties—the loss of large parts of Bosnia to his overlord, King Louis I of Hungary, and being briefly deposed by his magnates—Tvrtko's power grew considerably. He conquered some remnants of the neighbouring Serbian Empire in 1373, after the death of its last ruler and his distant relative, Uroš the Weak. In 1377, he had himself crowned king of Bosnia and Serbia, claiming to be the heir of Serbia's extinct Nemanjić dynasty.

As the Kingdom of Bosnia continued to expand, Tvrtko's attention shifted to the Adriatic coast. He gained control of the entire Primorje region and the major maritime cities of the area, established new settlements and started building a navy, but never succeeded in subjugating the lords of the independent Serbian territories. The death of King Louis and the accession of Queen Mary in 1382 allowed Tvrtko to take advantage of the ensuing succession crisis in Hungary and Croatia. After bitter fighting, from 1385 to 1390, Tvrtko succeeded in conquering large parts of Dalmatia, and Croatia proper. Following the Battle of Kosovo in 1389, his tenuous claim to Serbia became a mere fiction, as the Serbian rulers he sought to subdue became vassals of the victorious Ottoman Empire. The Ottoman Turks also launched their first attacks on Bosnia during Tvrtko's reign, but his army was able to repel them. Tvrtko's sudden death in 1391 prevented him from solidifying the Kotromanić hold on Croatian lands.

Croatian Littoral (Croatian: Hrvatsko primorje) is a historical name for the region of Croatia comprising mostly the coastal areas between traditional Dalmatia to the south, Mountainous Croatia to the north, Istria and the Kvarner Gulf of the Adriatic Sea to the west. The term "Croatian Littoral" developed in the 18th and 19th centuries, reflecting the complex development of Croatia in historical and geographical terms.

The region saw frequent changes to its ruling powers since classical antiquity, including the Roman Empire, the Ostrogoths, the Lombards, the Byzantine Empire, the Frankish Empire, and the Croats, some of whose major historical heritage originates from the area—most notably the Baška tablet. The region and adjacent territories became a point of contention between major European powers, including the Republic of Venice, the Kingdom of Hungary, and the Habsburg and Ottoman Empires, as well as Austria, the First French Empire, the Kingdom of Italy, and Yugoslavia.

The Austro-Turkish War, also known as the Habsburg–Ottoman War, was fought from 1788 to 1791, between the Habsburg monarchy and the Ottoman Empire. During the conflict, Habsburg armies succeeded in taking Belgrade (1789) and liberating much of central Serbia, also capturing several forts in central Croatia and in the Pounje region of the Ottoman Bosnia. Much of those gains were lost in the later stages of the war, that ended by the Treaty of Sistova (1791), with minor territorial changes in favor of the Habsburg side. The war was fought concomitantly with the Russo-Turkish War (1787–1792).

Slavonia (/sləˈvoʊniə/; Croatian: Slavonija) is, with Dalmatia, Croatia proper, and Istria, one of the four historical regions of Croatia. Located in the Pannonian Plain and taking up the east of the country, it roughly corresponds with five Croatian counties: Brod-Posavina, Osijek-Baranja, Požega-Slavonia, Virovitica-Podravina, and Vukovar-Syrmia, although the territory of the counties includes Baranya, and the definition of the western extent of Slavonia as a region varies. The counties cover 12,556 square kilometres (4,848 square miles) or 22.2% of Croatia, inhabited by 806,192—18.8% of Croatia's population. The largest city in the region is Osijek, followed by Slavonski Brod and Vinkovci.

Slavonia is located in the Pannonian Basin, largely bordered by the Danube, Drava, and Sava rivers. In the west, the region consists of the Sava and Drava valleys and the mountains surrounding the Požega Valley, and plains in the east. Slavonia enjoys a moderate continental climate with relatively low precipitation.

Lika (Croatian pronunciation: [lǐːka]) is a traditional region of Croatia proper, roughly bound by the Velebit mountain from the southwest and the Plješevica mountain from the northeast. On the north-west end Lika is bounded by Ogulin-Plaški basin, and on the south-east by the Malovan pass. Today most of the territory of Lika (Brinje, Donji Lapac, Gospić, Lovinac, Otočac, Perušić, Plitvička Jezera, Udbina and Vrhovine) is part of Lika-Senj County. Josipdol, Plaški and Saborsko are part of Karlovac County and Gračac is part of Zadar County, and it takes up about 12% of Croatia's land area.

Major towns include Gospić, Otočac, and Gračac, most of which are located in the karst poljes of the rivers of Lika, Gacka and others. The Plitvice Lakes National Park and Northern Velebit National Park are also in Lika.

Though the Republic of Croatia administratively consists of twenty counties, it is traditionally divided into four historical and cultural regions: Croatia proper, Dalmatia, Istria, and Slavonia. These are further divided into other, smaller regions.