Bonyads (Persian: بنیاد "Foundation") are charitable trusts in Iran that play a major role in Iran's economy. They control an estimated 20% of Iran's GDP, and are second only to the oil industry in manufacturing, trading, and real estate development in Iran. As of 2010, the largest bonyad is the Mostazafan Foundation, worth approximately $10 billion. In addition to large national bonyads like the Mostazafan Foundation, there are numerous bonyads affiliated with local clerics in "almost every" Iranian town. All are answerable only to the Supreme Leader of Iran. As of 2008, bonyads employ somewhere between 400,000 and 5 million Iranians.

Technically religious charitable organizations, they have evolved into "giant private monopolies with no governmental oversight", and are now described as channeling revenues to groups supporting the Islamic Republic, while providing limited and inadequate charity to the poor. Exempt from taxes and benefiting from "huge subsidies from government," they have been called "bloated," and "a major weakness of Iran's economy," that siphons off production to the lucrative black market.

Founded as royal foundations by Shah Mohammad Reza Pahlavi, the original bonyads were criticized for providing a "smokescreen of charity" to patronage, economic control, for-profit wheeling and dealing done with the goal of "keep[ing] the Shah in Power." Resembling more a secretive conglomerate than a charitable trust, these bonyads invested heavily in property development, such as the Kish Island resort; but the developments' housing and retail was oriented to the middle and upper classes, rather than the poor and needy.

After the 1979 Iranian revolution, the bonyads were nationalized and renamed with the declared intention of redistributing income to the poor and families of martyrs, i.e. those killed in the service of the country. The assets of many Iranians whose ideas or social positions ran contrary to the new Islamic government were also confiscated and given to the bonyads without any compensation.

Today, over 100 bonyads exist, and they are criticized for many of the same reasons as their predecessors. They form tax-exempt, government subsidized, consortiums receiving religious donations and answerable directly (and only) to the Supreme Leader of Iran. The bonyads are involved in everything from vast soybean and cotton fields to hotels to soft drinks to auto-manufacturing to shipping lines. The most prominent, the Bonyad-e Mostazafen va Janbazan, (Foundation for the Oppressed and Disabled), for example, "controls 20% of the country's production of textiles, 40% of soft drinks, two-thirds of all glass products and a dominant share also in tiles, chemicals, tires, foodstuffs."

Some economists argue that its chair, and not the Minister of Finance or president of the Central bank, is considered the most powerful economic post in Iran. In addition to the very large national bonyads, "almost every Iranian town has its own bonyad," affiliated with local clerics.

Estimates of how many people the bonyads employ ranges from in excess of 400,000 to "as many as 5 million."

Bonyads also play a crucial role in the spread of Iranian influence through extensive transnational and international activities, including philanthropy and commerce as soft power as well as providing hard power support.