Most of Croatia's borders are Europe's oldest. This is particularly true for northern and western borders which are old and stable, while the eastern borders are a result of constant contraction and loss of territory that began with the expansion of the Turkish Empire and went on until 1945 when borders between the republics were drawn in Yugoslavia in the aftermath of World War II.
Borders with Serbia (Vojvodina) and Bosnia and Herzegovina are centuries-old historical borders, established for the most part after the wars with the Ottoman Empire in 1669 and 1718. Those were the borders of Croatia when it joined the kingdom of Serbs, Croats and Slovenes in 1918. After the Second World War, the borders were somewhat modified to reflect the demographics of the time - as a rule at Croatia's expense. The most extensive changes involved borders with Serbia and Montenegro and, to a lesser degree, the border with Bosnia and Herzegovina.
The longest Croatian border is the one with Bosnia and Herzegovina which is 1,009.1 kilometers long, followed by borders with Slovenia at 667.8 kilometers, Hungary at 355.5 kilometers and FRY at 340.2 kilometers (317.6 km with Serbia and 22.6 km with Montenegro).

Maritime border of the Republic of Croatia is 948 kilometers long and is recognized by international law which defines the territorial sea as a zone 12 nautical miles wide as measured from any point of the shoreline or from any of the Croatian islands, i.e. from any point on the line that joins the most prominent parts of Croatian soil. Of the total length of maritime border, the border with the territorial seas of neighboring countries accounts for 66.75 kilometers, to wit: 27.1 kilometers with Italy, 12.1 kilometers with Slovenia and 27 kilometers with FRY/Montenegro. The demarcation line with Bosnia and Herzegovina within the internal waters of the Republic of Croatia accounts for 15 kilometers of maritime border. The long, well-indented shoreline - 1,777 kilometers as the crow flies - and the islands jutting deeply into the Adriatic Sea, constitute a large marine system that fully belongs to the Republic of Croatia.

Extreme geographical points of the Republic of Croatia

North - Žabink (County of Međimurje): 46*33' N i 16*22' E
South - Island Galijula (County of Dubrovnik-Neretva): 42*23' N i 16* 21' E
East - Rađevac (County of Vukovar-Srijem): 45*12' N i 19*27' E
West - Bašanija (County of Istria): 45*29' N i 13*30' E