Croatia–Slovenia border disputes

Border disputes and other unresolved issues between Slovenia and Croatia have existed since the two countries' independence following the breakup of Yugoslavia in 1991. The most notable border issue revolves around the boundary in the Gulf of Piran. Both nations have agreed to international arbitration.

According to the Croatian Bureau of Statistics, the two countries share about 668 kilometres (415 mi) of border. According to the Statistical Office of the Republic of Slovenia, the border spans 670 km (416 mi). The border runs in the direction from the southwest to the northeast.

The situation became more complex when the dispute nearly derailed Croatia's application to join NATO. It escalated further with Slovenia's blockade of Croatia's EU accession from December 2008 until September–October 2009, when Slovenia (a European Union member state) blocked the negotiation progress of Croatia (at the time an EU candidate state).

In on 4 November 2009 an arbitration agreement between Croatia and Slovenia was finally signed by the EU President and both countries' prime ministers, and a subsequent referendum in Slovenia authorized the use of binding arbitration.

On 28 July 2015, Croatia withdrew from arbitration after breaches of arbitration rules by Slovenia.

Following World War II, the area from north of Trieste to the Mirna River in the south was part of the Free Territory of Trieste. In 1954, the Territory was dissolved; the area was provisionally divided between Italy and Yugoslavia, and the division made final by the Treaty of Osimo in 1975.

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