Sattareh Farman Farmaian, the daughter of a Persian prince who used her family’s power to found a trailblazing social welfare movement on behalf of women, children, prisoners and other disadvantaged Iranians in the years before the Islamic revolution, died May 21 at her home in Los Angeles.

She was 90 and had lymphoma, said her daughter Mitra Jordan.

Ms. Farman Farmaian had lived in Los Angeles since supporters of Ayatollah Ruhollah Khomeini overthrew Mohammad Reza Pahlavi, the Western-backed shah, in 1979. In a widely read memoir, “Daughter of Persia” (1992), Ms. Farman Farmaian wrote that she narrowly escaped execution after being denounced for her progressive social work, which included the establishment of family planning clinics across Iran and a pioneering school of social work in the capital.

By the time of her exile, Ms. Farman Farmaian was widely regarded as the “mother of social work” in Iran, said Ahmad Karimi-Hakkak, director of the Roshan Center for Persian Studies at the University of Maryland.

Ms. Farman Farmaian was a powerful and, in some ways, unexpected heroine of the Iranian underclass. She was one of three dozen children born to a prominent prince in the Qajar dynasty that ruled Iran for more than a century. The dynasty came to an end when Reza Khan (later Reza Shah Pahlavi) staged a coup d’etat in 1921 — the year of Ms. Farman Farmaian’s birth.

The upheaval meant the end of her family’s formal authority but not its influence in Iranian high society. Ms. Farman Farmaian grew up in her father’s harem in Tehran, a milieu with 1,000 servants, opulent gardens and shimmering pools.

Unlike many other princes of the era, her father encouraged a worldly education for his children, including his daughters. Ms. Farman Farmaian attended an American Presbyterian school, where she sweated in her Girl Scout uniform in the Iranian heat.

Despite her affluent upbringing, Ms. Farman Farmaian frequently came into contact with the poor and underprivileged. During a school outing at 18, she had an epiphany.

“All at once I realized what I must have known forever,” she wrote in her memoir. “That I must have more education, that whatever else happened to me, to serve Iran and its people was my destiny.”

Ms. Farman Farmaian persuaded her family to allow her to enroll at the University of Southern California during World War II — an almost unheard-of undertaking for a young Iranian woman of her generation. She received a bachelor’s degree in sociology in 1946 and a master’s degree in social work in 1948.

In 1958, when she returned to Iran, she opened and became the first director of the Tehran School of Social Work. She had to create a Farsi word for “social worker,” she wrote in her memoir, because no such term existed. In addition to training students in the field, the school built community welfare clinics dedicated to literacy, child care and women’s health.

Ms. Farman Farmaian also helped found the Family Planning Association of Iran. Her organizations served a wide range of people throughout Iran, including orphans, hospital patients and prostitutes.

Much of this work was made possible by her prominence and connection to Iranian leaders, including the shah and his wife, Empress Farah, who offered financial support to the welfare clinics built by Ms. Farman Farmaian’s school.

Reviews of her memoir, written with Dona Munker, describe the book as “riveting” and “beautifully written.” But literature scholar Nasrin Rahimieh, reviewing the book in The Washington Post, also wrote that Ms. Farman Farmaian was “completely unprepared for the 1979 revolution” that overthrew the shah and led to her ultimate return to the United States.

While Ms. Farman Farmaian’s institutions no longer exist in their original forms, Karimi-Hakkak said, many of their social welfare functions continue to be carried out under the Islamic government.

Sattareh Farman Farmaian was born Dec. 23, 1921, in what she described as the “rose-perfumed” city of Shiraz. Her first attempt to study abroad, during World War II, ended when her ship was torpedoed by the Japanese en route to the United States. She tried again months later and arrived in Los Angeles on Independence Day 1944.

Before returning to Iran in 1958, she worked for about a decade in Los Angeles as a social worker and, later, for the United Nations in Iraq, where she sought to help settle nomadic tribes. She continued working with disadvantaged communities in Los Angeles after her return to the city in 1979.

Her marriage to Arun Chaudhuri, a film student she met at the University of Southern California, ended in divorce. Survivors include her daughter, Mitra Jordan of Bellevue, Wash.; two grandchildren; and many brothers and sisters.

“Long ago I set out into the world with my arms wide open,” Ms. Farman Farmaian wrote in her memoir, describing the tumultuous history of her country and her own life, “and I am sure that if I had it to do all over again, I would.”