International relations between the Republic of Chile and the Argentine Republic have existed for decades. The border between the two countries is the world's third-longest international border, which is 5,300 km (3,300 mi) long and runs from north to south along the Andes mountains. Although both countries gained their independence during the South American wars of liberation, during much of the 19th and the 20th century, relations between the countries were tense as a result of disputes over the border in Patagonia. Despite this, Chile and Argentina have never been engaged in a war with each other. In recent years, relations have improved. Argentina and Chile have followed quite different economic policies. Chile has signed free trade agreements with countries such as China, the United States, Canada, South Korea, as well as European Union, and it's a member of the APEC. Argentina belongs to the Mercosur regional free trade area. In April 2018, both countries suspended their membership from the UNASUR.

The Argentina–Chile border is the longest international border of South America and the third longest in the world after the Canada–United States border and the Kazakhstan–Russia border. With a length of 5,308 kilometres (3,298 mi), it separates Argentina from Chile along the Andes and on the islands of Tierra del Fuego. However, there are some border disputes, particularly around the Southern Patagonian Ice Field. It is the largest border of the two countries, beating the Argentina–Paraguay and Chile–Bolivia, Argentina's and Chile's second largest borders, respectively.