Kenya and South Sudan share a straight-line border that extends for over 200 km from the tripoint with Uganda in the south to the tripoint with Ethiopia in the north or east. Over two-thirds of its length is in dispute, making up an area known as the Ilemi Triangle. The conflict stems from ill-defined British colonial boundaries, and the disputed area was originally between the British colony of Uganda and the Anglo–Egyptian Condominium of Sudan. The Ugandan Rudolf Province was transferred to Kenya Colony in 1926, and the remote and poorly delineated Ilemi Triangle went with it. South Sudan inherited the dispute from Sudan after its independence in 2011.

The Ilemi Triangle has historically been divided by a variety of survey, patrol, and administrative lines throughout the colonial period, many of which are known by the color on which they appeared on maps of the era. The initial, vague international boundary defined between Uganda and Sudan in 1914 still characterizes South Sudan’s claim to the Ilemi Triangle. Kenya maintains de facto control of the entire area, all the way up to what is known as the 1950 Sudanese Patrol Line. Between these two extremes, there are at least two other commonly mapped “boundary” lines known as the 1938 Red Line and 1947 Blue Line, both of which were established under British oversight to better demarcate the grazing grounds of the Kenyan Turkana pastoralist peoples to which the original 1914 border vaguely referenced.

Instability and lack of resources have characterized the failure of a resolution to the Kenya–South Sudan boundary dispute. There were attempts during the colonial era to settle the territorial conflict, but solutions were almost impossible to implement due to the broader geopolitical picture. In the 20th century, the dispute involved not only Kenya, Sudan, and the UK, but also Uganda, whose nomadic peoples utilized the Ilemi Triangle, and Ethiopia, an independent empire with its own territorial aspirations, and Egypt, who had partial control of Sudan. Today, the dispute involves Kenya, South Sudan, and Ethiopia, but regional conflict, the importance of maintaining territory, and the possibility of natural resources present in remote Ilemi, have continued to make the dispute difficult to resolve.