The Eswatini–South Africa international boundary was first established during the colonial era as part of a broader British agreement describing the boundaries of the South African Republic (also known as Transvaal). There are no known modern agreements between South Africa and Eswatini, formerly Swaziland, regarding the course of the border. It extends for 444 kilometers (276 miles) from the first, southern tripoint with Mozambique west and north to the second, northern tripoint with Mozambique.

Eswatini claims large sections of South African territory based on the historic extent of Swazi control during the early 19th century. Despite negotiations in the 1980s, there has been little progress in resolving the boundary dispute. Nevertheless, South Africa and Eswatini share generally stable relations and are both members of the Southern African Development Community and the Southern African Customs Union.