Between 2010 and 2020, five Iranian nuclear scientists (Masoud Ali-Mohammadi, Majid Shahriari, Darioush Rezaeinejad, Mostafa Ahmadi Roshan, and Mohsen Fakhrizadeh) were killed in foreign-linked assassinations. Rezaeinejad was shot dead by gunmen on motorcycles, while Shahriari and Ahmadi Roshan were killed by explosives attached to their cars. Fereydoon Abbasi was also targeted in a car bombing, but survived.

The Iranian government accused Israel of complicity in the killings in order to disrupt Iran's nuclear program. In 2011 and 2012, Iranian authorities arrested a number of Iranians alleged to have carried out the assassination campaign on behalf of Mossad (the Israeli intelligence service). Western intelligence services and U.S. officials reportedly confirmed the Israeli connection. Israeli defense minister Moshe Ya'alon said: "We will act in any way and are not willing to tolerate a nuclear-armed Iran. We prefer that this be done by means of sanctions, but in the end, Israel should be able to defend itself."

The assassination campaign was reportedly terminated in 2013 following diplomatic pressure from the United States, which was attempting to negotiate restrictions on Iran's nuclear activities. According to NBC, two US senior officials confirmed that the People's Mujahedin of Iran (MEK) was "financed, trained, and armed by Israel" in killing Iranian nuclear scientists, although a Senior State Department Official later denied saying the MEK was not involved in the assassinations of Iranian nuclear scientists.

Seven incidents are listed here, including one in which the victim survived, and one where assassination has not been confirmed.

Date	Victim	Expertise	Method and location	Outcome
15 January 2007	Ardeshir Hosseinpour	Professor, authority on electromagnetism	By gas or possibly radiation poisoning, in Shiraz	Died
12 January 2010	Masoud Ali-Mohammadi	Professor, quantum field theorist and elementary particle physicist	By a remote-control bomb attached to a motorcycle, in Tehran	Assassinated
29 November 2010	Majid Shahriari	Nuclear engineer specialized in neutron transport	By a bomb attached to his car from a motorcycle, in Tehran	Assassinated
29 November 2010	Fereydoon Abbasi	Professor, nuclear physicist and administrator	By a bomb attached to his car from a motorcycle, in Tehran	Survived
23 July 2011	Darioush Rezaeinejad	Physicist, expert in neutron transport	Shot by motorcycle gunmen, in Tehran	Assassinated
11 January 2012	Mostafa Ahmadi Roshan	Professor, researching the making of polymeric membranes for gaseous diffusion, part of a process for uranium enrichment	By a bomb attached to his car from a motorcycle, in Tehran	Assassinated
27 November 2020	Mohsen Fakhrizadeh	Professor, nuclear physicist and head of Iran's nuclear program	Shot by a remote-control machine gun, in Damavand	Assassinated

On 15 January 2007, Ardeshir Hosseinpour, a professor at Shiraz University, was initially reported to have died of "suffocated by fumes from a faulty gas fire in sleep". Later reports indicated foul play. American private intelligence company Stratfor released a report on 2 February 2007 in which the claim was made, based on "sources very close to Israeli intelligence," that the victim was "in fact a long-time Mossad target."

In 2014, Ardeshir's sister, Mahboobeh Hosseinpour, interviewed from Turkey in a conversation arranged by "The New Iran" opposition group, claimed that her brother was murdered by Iran's Revolutionary Guards rather than by Israel, for refusing to participate in "Iran's nuclear enrichment program whose use was for atomic [weapons] purposes." According to Stratfor, Hosseinpour died of radiation poisoning.

On 12 January 2010, Masoud Ali-Mohammadi, a professor of physics at the University of Tehran, was killed by a remote-controlled bomb attached to a motorcycle parked near his car. The bomb exploded on the street outside his home in the Gheytariyeh neighbourhood of northern Tehran as he left for work. Two other people were wounded in the blast, which shattered windows in a nearby four-story building, damaged window frames and blew a garage door out of its frame. The BBC reported that neighbors assumed the jolt was caused by an earthquake. Iran blamed Israel and the U.S for the attack.

In January 2011, Iran announced that it had arrested 10 Iranian citizens who had worked with Mossad to carry out the assassination. State television broadcast a confession by Majid Jamali Fashi, who said he acted on the instructions of Mossad and had been trained in Tel Aviv: "I woke up at 4 and made a call, the plan had not changed. I parked the motorbike near the tree," Fashi said in his confession. Ali-Mohammadi's wife said, "I heard the explosion just when I closed the door." Later confirmed genuine by Western intelligence officials, Fashi was executed by Iran in May 2012.

According to Iranian media, Maziyar Ebrahimi was an alleged perpetrator code-named Amiryal (Persian: "امیریل") Maziyar Ebrahimi was later exonerated and explained eight years later how he was proved to be innocent in an interview. Ebrahimi told the BBC that Iran had tortured him into confessing he was a spy.

On 29 November 2010, Majid Shahriari, a professor at Shahid Beheshti University was killed by a bomb launched from a motorbike. The assassins had attached a bomb, detonating it from a distance. Shariari's wife, Ghasemi, was a passenger in the car and was injured in the explosion.

"I attached the bomb to the right front door and moved away quickly," said Arash Kerhadkish, who was convicted of assassinating Shahriari. One member of the assassination team was knocked from his motorcycle by the force of the blast. "The motorcycle fell down and one of the riders was injured. We helped him," said Maryam Izadi, a convicted member of the team, under interrogation.

In an almost simultaneous bomb attack, Fereydoon Abbasi, a professor at Shahid Beheshti University, where Shahriari also taught, and his wife were injured. "I had a meeting with Dr. Shahriari at the early morning. ... The bomb was attached to my car at 7:42. We were around the university square and I heard the sound of something colliding with my car and looked back and saw a motorbike. I concluded that that thing colliding with the car was [a] bomb. I stopped at once and told my wife to get out." According to his wife, Abbasi sustained facial and hand injuries.

On 23 July 2011, Darioush Rezaeinejad was shot five times and killed by motorcycle-riding gunmen in front of his home while he was with his wife after they picked up their daughter from kindergarten. His wife was also wounded in the attack.

The attack was described by an Israeli intelligence interviewed by Der Spiegel as "the first public operation by new Mossad chief Tamir Pardo". Rezaeinejad's wife, Shohreh Pirani, was also wounded in the attack. "I got off quickly and followed the shooter. After running several meters, I realized that they were shooting at me. I fell down and heard the motorcycle go away," she later said.

Initial reports said the gunmen had killed 35-year-old "Darioush Rezaei," a physics professor whose area of expertise was neutron transport, and who was linked to Iran's nuclear program. The victim was subsequently identified as Rezaeinejad, a postgraduate electrical engineering student at Tehran's K.N.Toosi University of Technology, who was expected to defend his thesis and working at a "national security research facility."

After the assassination, the speaker of Iran's parliament Ali Larijani stated that the United States and Israel had killed Rezaeinejad. The U.S. government, through State Department spokeswoman Victoria Nuland, rejected the accusation.

On 11 January 2012, Mostafa Ahmadi Roshan was assassinated with a "magnetized explosive" attached to the side of his car on his way to work, on the second anniversary of Masoud Ali-Mohammadi's murder at 8:30 am in Shahid Golnabi Street, Seyed Khandan, eastern Tehran.

According to Western intelligence sources, Ahmadi Roshan was "a victim of Israel's Mossad." "In this location, we reached the car and attached the bomb to the car and the bomb exploded near the white fence," said Arash Kerhadkish, under interrogation, as reported by the Mehr News Agency.

On 27 November 2020, the alleged head of Iran's nuclear weapons program, Mohsen Fakhrizadeh, was assassinated. Mohammad Javad Zarif, Iran's foreign minister, suggested that Israel was behind Fakhrizadeh's assassination.

There has been speculation about the identity of the perpetrators. Israel's Mossad was seen by Iran as the most likely candidate. Other suspects included Iranian opposition groups such as MEK, intelligence operatives from Arab countries opposed to the Iranian government, and the United States.

Iran blamed Israel and the U.S. for the assassinations. Secretary of State Hillary Clinton categorically denied any U.S. role in the killings, a denial called "plausible" by analysts given the reported lack of U.S. intelligence assets in Iran. Israel neither confirmed nor denied its role in the killings.

In early 2011, Majid Fashi confessed to the killing of Masoud Alimohammadi on Iranian state television, saying that he had trained for the operation at a Mossad facility near Tel Aviv. Fashi was executed in May 2012. That month, Iranian authorities announced the arrest of another 14 Iranians – eight men and six women – described as an Israeli-trained terror cell responsible for five of the attacks on Iranian scientists. Iran's IRTV Channel 1 broadcast a half-hour documentary, Terror Club, which included "the televised confessions of the 12 suspects allegedly involved in the killings of Ali-Mohammadi, Shahriari, Rezaeinejad, and Roshan, and the attempted killing of Abbasi."

According to Time, Western intelligence officials confirmed the cracking of two Mossad-backed espionage rings by Iranian intelligence. Officials in the Obama administration also reportedly confirmed Israeli involvement. According to Dan Raviv, Mossad officials were "pissed off and shocked" to see their intelligence assets paraded on Iranian television. After the arrests, Iran said it was confident it had arrested all those responsible for the attacks. Time said that Iran attempted to retaliate against Israel for the assassinations by launching up to 20 hastily-organized attacks on Israeli diplomatic missions around the world in 2012, none of which were successful.

Israel has never publicly confirmed or denied responsibility for the assassinations, and Israeli officials have expressed readiness to employ all necessary means in the nation's defence.

Israeli defence minister Moshe Ya'alon said in an interview with Der Spiegel, "Ultimately it is very clear, one way or another, Iran's military nuclear programme must be stopped ... We will act in any way and are not willing to tolerate a nuclear-armed Iran. We prefer that this be done by means of sanctions, but in the end, Israel should be able to defend itself." Ya'alon added that he was not responsible "for the life expectancy of Iranian scientists."

The assassination campaign against Iranian nuclear scientists reportedly ended in 2013 following pressure on Israel from the Obama administration to stop the attacks during negotiations with Iran to restrict its nuclear programme. Mossad officials also reportedly concluded that the attacks were "too dangerous" for valuable intelligence operatives in Iran. The organisation has since reportedly instructed its Iranian spy network to concentrate on finding evidence of Iranian breaches of its nuclear-restriction agreements.

Although Iran ostensibly considers Israel responsible for the 2010–12 assassination campaign against Iranian nuclear scientists, uncertainty surrounds the 2007 death of Iranian scientist Ardeshir Hosseinpour. Hosseinpour was reported by Iranian authorities to have died from gas poisoning caused by a faulty heater, but a six-day delay in their announcement raised suspicions outside Iran. According to Stratfor, Hosseinpour was assassinated by Mossad using radiation poisoning; Iranian officials denied this, calling their scientists "safe." In 2014 Hosseinpour's sister, Mahboobeh, accused the Iranian Revolutionary Guard of killing him for his alleged refusal to work on Iran's nuclear-enrichment program. Mahboobeh said that she obtained the information from Ardeshir's widow.

Opposition sources in Iran have say that the Iranian government assassinated Massoud Ali-Mohammadi because he was one of their supporters.

The U.S. government condemned the assassinations without implicating any party. However, some American politicians supported the killings. Former speaker of the House Newt Gingrich supported "taking out [Iranian] scientists," and presidential candidate Rick Santorum called the killings "a wonderful thing."

Israel Defense Forces spokesman General Yoav Mordechai said that he had "no idea who targeted [Mostafa Ahmadi Roshan] but I certainly don't shed a tear." Mehdi Hasan wrote in The Guardian, "These 'men on motorbikes' have been described as 'assassins'. But assassination is just a more-polite word for murder ... How many more of our values will we shred in the name of security? Once we have allowed our governments to order the killing of ... fellow human beings, in secret, without oversight or accountability, what other powers will we dare deny them?"

Historian Michael Burleigh compared the assassinations to the Allied bombing of Nazi V2 rocket sites during World War II, noting that the bombers "were not unduly concerned whether scientists and engineers were killed too, nor foreign slave labourers provided the V2s ceased raining down on London." According to Burleigh, scientists are not abstract researchers; there are "real world" consequences of their actions, and he "shall not shed any tears whenever one of these [Iranian] scientists encounters one of the unforgiving men on motorbikes ... Except that if Israel ventures down this road, I cannot think of much of an argument to prevent Iran following them, and then anyone else who decides to follow."

Paul Koring wrote that the assassinations have reportedly had a "chilling impact" on the Iranian scientific community, making it "more difficult for the regime to recruit anyone [for] national-security research efforts". Koring also wrote that the assassinations, regardless of their effectiveness, "left a real trail of grief". Koring cited Shorheh Pirani, the widow of Darioush Rezaeinejad, who was gunned down in front of his wife and five-year-old daughter. A year after the assassination, he wrote that Armita "still draws pictures of her father. In them, she and her mother always have their mouths open in terrified screams. 'Every day', Mrs. Pirani said, 'she makes that painting.'"

Supreme Leader of Iran Ali Khamenei condemned the attacks, saying "the heinous crimes of those who try to suppress the scientific growth of the Iranian nation have been exposed. But there is no doubt that in the face of animosity, Iranian scientists, professors, and researchers will thwart the [enemy's] vicious plans... The martyrdom of these eminent scientists ... has honored the scientific community." Earlier, the leader had stated that "with their achievements, young Iranian scientists have guaranteed the future and long term energy supply for the nation, and such advancements should not be lost at any cost."

In an interview with Israeli journalist Ronen Bergman, former CIA director Michael Hayden said that the most effective method employed to stop the Iranian nuclear program had been the assassinations of Iranian nuclear scientists. The assassinations eliminated people with valuable knowledge and experience and forced the Iranian government to implement strict security measures such as hunting for Mossad moles, screening equipment for viruses, and assigning bodyguards to scientists, which delayed the program by years, and caused many Iranian scientists to leave the program out of fear that they could be targeted.

• Assassination and terrorism in Iran
• Assassination of Ali Sayyad Shirazi
• Targeted killings by Israel Defense Forces
• Dariush Rezaeinejad
• 2020 Iran explosions
• Gerald Bull