Croatia–Slovenia border disputes

Following the breakup of Yugoslavia in 1991, Slovenia and Croatia became independent countries. As the border between the countries had not been determined in detail prior to independence, several parts of the border were disputed, both on land and at the sea, namely in the Gulf of Piran.

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 mostly runs along a southwest-northeast axis.

The countries have attempted to resolve the dispute, most notably with the Drnovšek–Račan agreement in 2001 that was ratified by Slovenia but not by Croatia. Because of the disputed border, Slovenia blocked Croatia's EU accession talks until the agreement was reached by both countries and the EU to settle the dispute by a binding arbitration.

On 29 June 2017, the Permanent Court of Arbitration issued a binding ruling on the border, ruling on the disputed parts of land border, drawing the border in the Gulf of Piran, and ruling that Slovenia should have direct access to international waters in the north Adriatic Sea using a corridor crossing Croatian waters. It also ruled on several other disputed border areas. The ruling was hailed by Slovenia but Croatia said it would not implement it. Croatia stated that they withdrew from the process in 2015, citing the discovered talks between the Slovenian government representative and the member of the arbitration court as a breach of the arbitration rules. Slovenia implemented the ruling on 29 December 2017 with continued opposition from Croatia.