Fordow Fuel Enrichment Plant (FFEP) is an Iranian underground uranium enrichment facility located 20 miles (32 km) northeast of the Iranian city of Qom, near Fordow village, at a former Islamic Revolutionary Guard Corps base. The site is under the control of the Atomic Energy Organization of Iran (AEOI). It is the second Iranian uranium enrichment facility, the other one being that of Natanz. According to the Institute for Science and International Security, possible coordinates of the facility's location are: 34°53′05″N 50°59′45″E / 34.88459°N 50.99596°E / 34.88459; 50.99596.

Existence of the then-unfinished enrichment plant was disclosed to the International Atomic Energy Agency (IAEA) by Iran on 21 September 2009, but only after the site became known to Western intelligence services. Western officials strongly condemned Iran for not disclosing the site earlier; U.S. President Barack Obama said that Fordow had been under U.S. surveillance. Iran argues that this disclosure was consistent with its legal obligations under its Safeguards Agreement with the IAEA, which Iran claims requires Iran to declare new facilities 180 days before they receive nuclear material. However, the IAEA stated that Iran was bound by its agreement in 2003 to declare the facility as soon as Iran decided to construct it.

In its initial declaration, Iran stated that the purpose of the facility was the production of UF₆ enriched up to 5% U-235, and that the facility was being built to contain 16 cascades, with a total of approximately 3000 centrifuges. Later, in September 2011, Iran said it would move its production of 20% LEU to Fordow from Natanz, and enrichment started in December 2011. In January 2012, the IAEA announced that Iran had started producing uranium enriched up to 20% for medical purposes and that material "remains under the agency's containment and surveillance.”

Under the Joint Comprehensive Plan of Action of April 2015, the Fordow plant was to be restructured to less intensive research use. The Fordow facility was to stop enriching uranium and researching uranium enrichment for at least fifteen years, and the facility was to be converted into a nuclear physics and technology centre. For 15 years, it would maintain no more than 1,044 IR-1 centrifuges in six cascades in one wing of Fordow. "Two of those six cascades will spin without uranium and will be transitioned, including through appropriate infrastructure modification," for stable radioisotope production for medical, agricultural, industrial, and scientific use. "The other four cascades with all associated infrastructure will remain idle." Iran is not permitted to have any fissile material in Fordow.

Under the terms of the nuclear agreement with Iran, two-thirds of the centrifuges inside Fordo have been removed in recent months, along with all nuclear material. The facility is banned from any nuclear-related work and is being converted to other uses, eliminating the threat that prompted the attack plan, at least for the next 15 years.

— The New York Times, February 16, 2016

In 2018, the Israeli company ImageSat published satellite photographs showing renewed construction and development at the Fordow facility.

On 5 November 2019, Iranian nuclear chief Ali Akbar Salehi announced that Iran will enrich uranium to 5% at Fordow.

In January 2020 the Fordow site had 1,044 centrifuges designed to enrich uranium hexafluoride.

In January 2021 the Fordow site began to produce uranium enriched to a 20% level.

In March 2023 CNN reported that "near bomb-grade" uranium had been found at Fordow. The IAEA confirmed that 83.7% pure U238 was discovered at Fordow, and that this had been very much a surprise to the agency.

In June 2024 the IAEA remarked that Iran had built additional centrifuges, while the Washington Post remarked on the Iranian order to triple the centrifuge capacity of the Fordow plant. The Times of Israel said that four new cascades had been installed but had not yet been commissioned.

Google Maps satellite images for the Fordow site can be found at coordinates 34.885649,50.99669. Images zoomed to the 20 meter level show a large double fence perimeter border erected around the site with towers located every 25 meters. Six 10 meter wide entry portals to the complex are located within the fenced area, as well as several buildings, the largest of which is approximately 5,500 square metres (59,000 sq ft).

Iranian authorities state the facility is built deep in a mountain because of repeated threats by Israel to attack such facilities, which Israel believes can be used to produce nuclear weapons. However, attacking a nuclear facility so close to the city of Qom which is considered so holy between Shia Muslims brings concern of a potential risk of a Shiite religious response.

In November 2013, hundreds of Iranians, mostly students of Sharif University of Technology, accompanied by the head of AEOI, Ali Akbar Salehi, and several Majles (parliament) representatives formed a human chain around the Fordow uranium enrichment facility. The students were there to show their support for the Iranian nuclear program.

In 2016, Iran stationed anti-aircraft S-300 missile system at the site.

In February 2023 the IAEA remarked that the Fordow plant had changed.

• Natanz Nuclear Facility

• David Albright, Frank Pabian, and Andrea Stricker: The Fordow Enrichment Plant, aka Al Ghadir: Iran’s Nuclear Archive Reveals Site Originally Purposed to Produce Weapon-Grade Uranium for 1–2 Nuclear Weapons per Year – Institute for Science and International Security, March 13, 2019

34°53′04″N 50°59′53″E / 34.8845°N 50.9981°E / 34.8845; 50.9981