Sources:[2][3] Until 1991, it was the border between Italy and Yugoslavia.

When Slovenia gained independence in 1991, it became the Italian–Slovenian border.

Between 1920 and 1947 the border between Italy and Kingdom of Yugoslavia went further east.

The definition of the border between Italy and Yugoslavia dates back to the Treaty of Peace with Italy, 1947.

[1] Some changes were made in 1954 (when the Free Territory of Trieste was divided between Italy and Yugoslavia), 1975 (Treaty of Osimo, some adjustments)[4] and 2017 (slight change to reflect current course of a river).