|Highly enriched uranium (HEU) is one of the most dangerous materials in the world, because it is a key ingredient in making a nuclear bomb. If a terrorist organisation can get HEU, it would be close to making a nuclear bomb. After South Africa disarmed its nuclear weapons, it kept HEU that was extracted from the nuclear bombs. The US tried to persuade South Africa to blend down its HEU into low enriched uranium (LEU) or give it up for safekeeping. However, South Africa refused to give it up. After a breach at Pelindaba, a national key point facility where South Africa stores its HEU, the US intensified its efforts to pressure South Africa to give its HEU up. It even promised incentives to South Africa should they agree to give it up, but South Africa refused. The US used the nuclear terrorism narrative to justify its initiative to eliminate vulnerable materials in the world. However, South Africa is yet to be swayed. This is odd since South Africa's refusal can negatively affect its credentials as a nuclear non-proliferation and disarmament champion and its image as a norm entrepreneur. The objective of the study was to understand the role played by HEU in South Africa's nuclear diplomacy. It was to explore HEU as a factor in the state's nuclear diplomacy and to understand the power of having HEU in nuclear negotiations, as well as what SA intends to do with its HEU. The study is framed theoretically by drawing on foreign policy theory, namely middle-power theory, and revisionism. It juxtaposed middle power, reformist, and revisionist positions with status quo foreign policy to analyse the role of HEU in South Africa's nuclear diplomacy. As a middle power with a moral high ground, South Africa hoped that it can affect change in the nuclear regime. However, when this did not occur its foreign policy shifted to a revisionist character that is discontent with the status quo in the nuclear regime. SA is dissatisfied with the current nuclear order and wants it revised towards liberal values such as equality and non-discrimination. It views the current nuclear order as nuclear apartheid. Therefore, South Africa uses HEU as leverage against nuclear weapon states in nuclear diplomacy. It is using HEU as an act of defiance against nuclear weapon states (such as the US) that are yet to disarm their nuclear weapons.