Hungary–Romania border

The Hungary–Romania border (Hungarian: Magyar–Román Államhatár; Romanian: Frontiera între Ungaria și România) refers to the state border between Hungary and Romania. It was established in 1920 by an international commission, the "Lord Commission", presided over by geographers including Emmanuel de Martonne and Robert Ficheux, and historians Robert William Seton-Watson and Ernest Denis. The border was set by the Treaty of Trianon which was signed on 4 June 1920.

The border has been stable since the end of the Second World War, when it received its current shape, and is no longer officially in dispute between the countries. In the current form, the border is about 448 kilometers long, or about 278 miles. It is demarcated by pillars, and about 20 kilometers of the border are marked by the Mureș River (”Maros” in Hungarian).

At the moment, the border is an internal border of the European Union, having once been an external border until Hungary's accession to the alliance on May 1, 2004. Romania followed suit, and became a member state of the European Union on January 1, 2007. Both countries later joined the Schengen Area (Hungary on December 21, 2007 and Romania on January 1, 2025), easing travel between the two.