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Iran-US relations have swung dramatically from early trust to outright hostility. Beginning in the mid-19th century with Qajar Persia, the US gained respect as a neutral outsider, with American advisers like Morgan Shuster and Arthur Millspaugh helping manage Persian finances. The alliance deepened after World War II, but the 1953 CIA-backed coup that overthrew Prime Minister Mohammad Mosaddegh set the stage for a close partnership with Shah Reza Pahlavi—a partnership that ended abruptly with the 1979 Iranian Revolution.

Since 1980, the two countries have had no formal diplomatic ties, with Pakistan and Switzerland serving as protecting powers. The US imposed a full trade embargo in 1995. Though the 2015 JCPOA nuclear deal briefly lifted sanctions, former President Trump's 2018 withdrawal re-imposed them, prompting Iran to breach enrichment limits. Tensions boiled over on February 28, 2026, when the US and Israel launched a joint attack on Iran, assassinating Supreme Leader Ali Khamenei and starting a war that ended with a June 2026 ceasefire mediated by Pakistan and Qatar.