Armenia–Azerbaijan border
40°18′N 45°50′E / 40.300°N 45.833°E
The Armenia–Azerbaijan border (Armenian: Հայաստան–Ադրբեջան սահման, romanized: Hayastan–Adrbejan sahman; Azerbaijani: Azərbaycan–Ermənistan sərhədi) is the international border between the Republic of Armenia and the Republic of Azerbaijan. Estimates of the border's length vary from 996 km (619 mi) to 1,007.1 km (625.8 mi). European routes E002 and E117 cross the border.
The de jure border follows that of the former Armenian Soviet Socialist Republic and the Azerbaijan Soviet Socialist Republic and consists of two main segments – that between Armenia and Azerbaijan's Nakhchivan exclave in the west, and the longer section between Armenia and 'mainland' Azerbaijan to the east. Additionally, there are a number of enclaves on either side of the boundary, however these no longer exist except in a de jure sense. The borders between Armenia and Azerbaijan have been closed since 1989 due to the Turkish and Azeri blockade of Armenia, which aimed to suppress the Karabakh Movement which called for independence from Azerbaijan and reunification with Armenia.
Following Armenia's defeat in the Second Nagorno-Karabakh War, a border crisis began with numerous instances of incursions and occupations by Azeri forces of Armenian territory. In October 2022, the two countries reached an agreement that Soviet-era borders should form the basis of border delineation based on the Alma-Ata 1991 Declaration, and Armenia returned four villages within Azerbaijan's de-jure border which Armenia controlled since 1990s. Azerbaijan continues to occupy 215 square kilometers of Armenian territory.