Iranian-Americans, also known as Persian-Americans, are United States citizens or nationals who are of Iranian ancestry or who hold Iranian citizenship. According to the National Organization for Civil Registration, an organization of the Ministry of Interior of Iran, the United States has the greatest number of Iranians outside the country.

Most Iranian-Americans arrived in the United States after 1979 in the wake of the Iranian Revolution and the fall of the Iranian monarchy. Over 40% of them settled in California, specifically Los Angeles, where they formed distinct ethnic enclaves, such as the Angelino community of "Tehrangeles" in Westwood, Los Angeles.

Research by the Iranian Studies Group at the Massachusetts Institute of Technology in 2004 estimated the number of Iranian-Americans at 691,000, about half of whom live in California.

"Iranian-American" is sometimes used interchangeably with "Persian-American", partly due to the fact that, in the Western world, Iran was known as "Persia". On the Nowruz of 1935, Reza Shah Pahlavi asked foreign delegates to use the term Iran, the endonym of the country used since the Sasanian Empire, in formal correspondence. Since then the use of "Iran" has become more common in Western countries. This also changed the usage of the terms for Iranian nationality, and the common adjective for citizens of Iran changed from "Persian" to "Iranian." In 1959, the government of Mohammad Reza Pahlavi, Reza Shah Pahlavi's son, announced that both "Persia" and "Iran" could officially be used interchangeably. The issue is still debated today.

Some wish to disassociate themselves from the Islamic Republic of Iran, yet this rationale has been criticized as the term "Iran" was widely used before 1979 as well. The term "Iranian" is regarded as more inclusive than "Persian", as the term "Persian" excludes non-Persian ethnic minorities of Iran. While the majority of Iranian-Americans come from Persian backgrounds, there is a significant number of non-Persian Iranians such as Azeris and Kurds within the Iranian-American community, leading some scholars to believe that the label "Iranian" is more inclusive, since the label "Persian" excludes non-Persian minorities.

One of the first recorded Iranians to visit North America was Martin the Armenian, an Iranian-Armenian tobacco grower who settled in Jamestown, Virginia in 1618. Mirza Mohammad Ali, also known as Hajj Sayyah, was an Iranian who came to North America in the 1800s. He was inspired to travel around the world due to the contradiction between the democratic ideals he read about and how his fellow Iranians were treated by their leaders. He began his travels as a 23-year-old looking for knowledge, to experience the lives of others, and to use that knowledge to help with Iran's progress. His stay in the United States lasted 10 years, and he traveled across the country from New York to San Francisco. He met a variety of influential American figures including President Ulysses S. Grant, who met with him on several occasions. On 26 May 1875, Hajj Sayyah became the first Iranian to become an American citizen. He was imprisoned upon his return to Iran for taking a stand against living conditions there. He looked to the United States to protect him but to no avail. During the peak period of worldwide emigration to the United States (1842–1903), only 130 Iranian nationals were known to have immigrated.

The first wave of Iranian migration to the United States occurred from the late 1940s to 1977, or 1979. The United States was an attractive destination for students, as American universities offered some of the best programs in engineering and other fields, and were eager to attract students from foreign countries. Iranian students, most of whom had learned English as a second language in Iran, were highly desirable as new students at colleges and universities in the United States. By the mid-1970s, nearly half of all Iranian students who studied abroad did so in the United States. By 1975, the Institute of International Education's annual foreign student census figures listed Iranian students as the largest group of foreign students in the United States, amounting to a total of 9% of all foreign students in the country. As the Iranian economy continued to rise steadily in the 70s, it enabled many more Iranians to travel abroad freely. Consequently, the number of Iranian visitors to the United States also increased considerably, from 35,088, in 1975, to 98,018, in 1977. During the 1977–78 academic year, of about 100,000 Iranian students abroad, 36,220 were enrolled in American institutions of higher learning. During the 1978–79 academic year, on the eve of the revolution, the number of Iranian students enrolled in American institutions rose to 45,340, and in 1979–80, that number reached a peak of 51,310. At that time, according to the Institute of International Education, more students from Iran were enrolled in American universities than from any other foreign country. The pattern of Iranian migration during this phase usually only involved individuals, not whole families. Due to Iran's increasing demand for educated workers in the years before the revolution, the majority of the Iranian students in America intended to return home after graduation to work, especially those who had received financial aid from the Iranian government or from industry on condition of returning to take jobs upon graduation. Due to the drastic events of the 1979 Revolution, the students ended up staying in the United States as refugees. These several thousand visitors and students unintentionally became the basis of the cultural, economic, and social networks that would enable large-scale immigration in the years that followed.

The second phase of Iranian migration began immediately before and after the Iranian Revolution of 1979 and the overthrow of the Shah Mohammad Reza Pahlavi, and became significant in the early 1980s. As Ronald H. Bayor writes, "The 1979 Revolution and the 1980–88 war with Iraq transformed Iran's class structure, politically, socially, and economically." The revolution drastically changed the pattern and nature of Iranian emigration to the United States, while the Iran-Iraq War that ensued afterwards was also another factor that forced many of the best-educated and most wealthy families into exile in the United States and other countries. Once basically an issue of brain drain during the Pahlavi period, it was now predominantly an involuntary emigration of a relatively large number of middle- and upper-class families, including the movement of a considerable amount of wealth. During and after the revolution, most students did not return to Iran, and those who did were gradually purged from the newly established Islamic Republic. Many students who graduated abroad after the revolution also did not return, due to the ruling clergy's repression. As a result, the educated elite who left Iran after the revolution, and the new graduates in the United States who chose not to return home, created a large pool of highly educated and skilled Iranian professionals in the United States. By 2002, an estimated 1.5 to 2.5 million Iranians lived abroad, mainly in North America and Europe, due to the Islamic government's authoritarian practices.