Abstract: This paper explores how the Iraq-Iran waterway border dispute played a key role in Cold War rivalries in the Middle East. Although the waterway border dispute between Iran and Iraq existed prior to the Cold War, the ascendancy of the Iranian Islamic Revolution led by Ayatollah Ruhollah Khomeini in 1979 undoubtedly proved a key element in igniting the war. United States military intrusion in the war was designed ostensibly to preserve and expand US political and economic security in the Middle East. While the US sought to maintain access to Middle Eastern oil, the Soviets worked desperately to exploit the chance to improve ties with Iran and Iraq and establish a position in the Gulf. The involvement of the Cold War superpowers directly influenced the duration and human cost of the war, including more than one million dead, approximately 800,000 injured, and more than one hundred thousand prisoners. Further, it came to be considered one of the most consequential wars for its vital repercussions for Iraq, Iran, and their relations with the US. This paper argues that the involvement of the United States and the Soviet Union in the Iran-Iraq War was rooted in their Cold War rivalry in the Middle East and particularly in the Persian Gulf. Their intervention took various forms, including economic, political, and military, and was based on numerous motivating factors. Description of the Topic: US-Soviet intervention in the Iran- Iraq War was prompted by the necessity of imperialism and Communism’s determination in the Persian Gulf. The ascendancy of the Iranian Islamic Revolution in 1979 threatened the geopolitical ambitions of the US and the Soviet Union and compelled the superpowers to support Iraq in the war. Likewise, the US also looked for a way to solve the American hostage crisis in Iran. Iran proved their hostility to the US yet also refused to cooperate with the Soviets. However, the Cold War rivalry led the superpowers to sell military equipment to both belligerents thereby expanding duration of the war and escalating the death toll. This paper considers the war's influence on relations between Iraq, Iran, Saudi Arabia, and the Soviet Union and its role in the United States’ increasingly global Cold War strategies. In such, this paper reveals the consequences of the war and how it became a significant factor in Cold War rivalries through the War on Terror.