The 9 Most Popular Conspiracy Theories in Recent History

Social media has helped amplify and circulate misinformation.
Princess Diana in a red and white hat

In the year 2021, conspiracy theories run rampant, from the halls of Congress to viral Facebook and blush-pink Instagram posts. Conspiracy theories are nothing new in the United States, says Cynthia Miller-Idriss, an American University sociology professor who focuses on extremism and radicalization, but they’ve been able to spread like wildfire over the past decade due to social media, which can easily amplify and circulate misinformation.

Amid a pandemic that has killed 600,000 Americans to date, conditions couldn’t be more ripe for conspiracy theories to take hold. Miller-Idriss says that people tend to turn to conspiracy theories when they’ve lost a sense of control and feel afraid and anxious because these theories can offer comfort in the form of a black-and-white answer. “When people feel out of control, they’re attracted to things that offer them an action path,” Miller-Idriss tells Teen Vogue. “It’s easier to believe in some nefarious orchestration than to believe that there is an invisible virus in the air that could harm their family.”

According to Miller-Idriss, “inexplicable deaths” — whether it’s death on a mass scale, like the pandemic, or the loss of a famous person like Princess Diana — breed conspiracy theories. “When something is so horrifying, it’s easier for people to believe it can’t be true. They can become more vulnerable to conspiracy theories because maybe they can’t psychologically wrap their head around the fact that it is true,” she says. “It’s these episodic, shocking events that create vulnerability."

There's also a long historical record of the U.S. government lying to its citizens, including about medical experiments, covert surveillance and torture programs, and the existence of weapons of mass destruction in Iraq. Harboring suspicions that the government isn't always telling the full story is a perfectly reasonable response to this pattern of deception. But sometimes critical thinking and skepticism blossom into something more fanciful and outlandish and a willingness to believe information that matches up with our preexisting political leanings or ideological beliefs. 

In Miller-Idriss's work as the director of American University’s Polarization and Extremism Research & Innovation Lab, she has found that one way to combat conspiracy theories is to reach people through a process called attitudinal inoculation. With this technique, researchers strive to teach people how propaganda, misinformation, and conspiracy theories function so that when they come across suspicious claims from dubious sources, they’re appropriately skeptical.

Below Teen Vogue takes a look at some of the most popular conspiracy theories of the past 50 years.

1. Myths about the Holocaust 

Between 1941 and 1945, six million Jews were killed across Europe in a horrific genocide led by Nazi dictator Adolf Hitler. Despite the fact that the Holocaust is one of the best-documented events in history, there are swaths of the population that don’t believe it happened — or they believe the death toll has been enormously inflated. One 2014 survey, coordinated by the Anti-Defamation League, of more than 53,000 people across 100 countries found that only 30% of respondents thought historical accounts of the Holocaust were accurate. Respondents under the age of 65 were more likely to say they didn’t believe the Holocaust happened as history books say it did.

Poor education on the subject may be one explanation for this, but some conspiracy theorists push the anti-Semitic notion that the Holocaust was invented or exaggerated to garner sympathy and monetary gains for Jewish people while serving and advancing Jewish interests. Deborah E. Lipstadt, a historian and professor who has written books on Holocaust denial, separates Holocaust deniers into two groups: There are the hard-core deniers who say the Holocaust didn’t happen at all; then, Lipstadt says, there are the less-fervent deniers who may admit the Holocaust happened but question the official death toll or that gas chambers were used for mass murder.

Among the many poignant points Lipstadt raises about Holocaust denial is this question: “For the deniers to be right, who has to be wrong? Well, certainly all the survivors… the bystanders… but most of all you have the perpetrators. They never said it didn’t happen.”

2. The CIA had a hand in JFK's assassination

Lee Harvey Oswald was arrested on November 22, 1963, for assassinating President John F. Kennedy Jr. that same day in Dallas, Texas. Two days later, while being transported to a local jail, Oswald was shot and killed by Jack Ruby, a Texas nightclub owner. This shocking set of events was ripe for conspiracies from the start: Not only was a handsome, popular president fatally shot in broad daylight, the accused assassin was killed days later, inviting speculation about a cover-up. As early as the late 1960s, more than 50% of Americans didn’t believe Oswald had acted alone. And as of 2017, FiveThirtyEight reports, 61% of Americans believed the assassination involved a conspiracy of some sort.

There are a few main JFK conspiracy theories. One popular theory is that the CIA killed JFK in retaliation for the failed Bay of Pigs invasion to overthrow Cuban leader Fidel Castro. According to biographer Philip Shenon, Bobby Kennedy, JFK's brother and the attorney general, initially thought a group of rogue CIA agents were involved in JFK's death, though he later reconsidered. Another theory is that Oswald wasn’t the lone gunman; people can hardly be faulted for believing this when a House of Representatives Select Committee on Assassinations found that there was “probably” a conspiracy involving a second shooter. In 1982, another committee called those findings into question, but the theory had already taken root. A third theory: The assassination was actually a mob hit meant to punish Bobby Kennedy for cracking down on the mafia. Oh, and did you hear the one about Ted Cruz’s father? We’re going to skip it here, but if you feel like a laugh, look into it.

3. The moon landing was faked

In July 1969, astronauts Neil Armstrong and Buzz Aldrin became the first humans to land on the surface of the moon — or did they? Just kidding. They absolutely did. But by the 1970s, 30% of Americans believed the moon landing had been faked. Alternative histories soon materialized. In the case of the “fake moon landing,” William Kaysing apparently started writing the book We Never Went to the Moon: America’s Thirty Billion Dollar Swindle as satire, but he ended up fully believing the conspiracy. The primary idea in his book was that the footage of astronauts taking their first steps on the moon’s surface — which hundreds of millions of people watched live on TV — was actually shot at Nevada’s Area 51 (another hotbed for conspiracy theorists).

As recently as 2019, a small survey showed that 10% of Americans still believed that the moon landing was a hoax. (In 2018, after NBA star Steph Curry said he didn’t believe in the moon landing, NASA offered him a lunar lab tour.)

4. Princess Diana’s death was no accident

When Princess Diana – a beautiful, young, royal outsider known as “the people’s princess” – was killed in a car crash in Paris in 1997, one year after her divorce from Prince Charles, conspiracies immediately abounded. The specifics vary, but the crux of most Diana-related theories is this: The car accident that killed her was not an accident. At the time of her death, she was dating Dodi Fayed, an Egyptian film producer who died in the limo alongside her, who was supposedly planning to propose to Diana the night of the accident. In a court witness statement, Dodi’s father, Mohamed al-Fayed, said they were killed because the monarchy couldn’t stand the thought of Diana and Prince Charles’s sons — heirs to the British throne — having a stepfather who was Egyptian and Muslim. Dodi’s father also claimed Diana was pregnant at the time of the crash, though the coroner who examined Diana said she was not.

Another theory is that the limo driver, Henri Paul, who was drunk at the time of the accident, intentionally crashed the car. Because Paul was the head of security at the Ritz Hotel in Paris, where the couple had departed from just prior to the crash, conspiracy theorists believe he might have been on the payroll of a national intelligence service group that wanted Diana dead. Other theorists believe that Diana’s medical care after the crash was deliberately sabotaged; for conspiracy theorists in the U.S., this idea arose from the differences between French and American approaches to emergency care. In France, protocol dictates that emergency medical personnel attempt to stabilize a patient before transferring to the hospital; in the U.S., getting to the hospital is the first priority. Because Diana was treated at the scene and not immediately rushed to the nearest hospital, some think this is proof she was purposefully killed.

5. 9/11 was an inside job

In a series of coordinated terror attacks, nearly 3,000 people lost their lives during the events of September 11, 2001, with thousands more injured and over 2,000 first responders eventually losing their lives due to illnesses related to their time working at Ground Zero. On that fall day in 2001, Americans watched, stunned, as two planes hit the Twin Towers in New York City, while a third struck the Pentagon in Washington, DC, and a fourth crashed into a field outside of Shanksville, Pennsylvania. September 11 took its place in history as the date of the most deadly foreign attack on American soil, usurping Pearl Harbor.

Maybe it’s because of the scale of loss — that nearly 3,000 people could be killed within a few hours on a sunny September morning — or because of the lies that have been told to the American people to sell them on the endless wars that followed the attacks, but the subject of 9/11 has always been a playground for conspiracy theorists. One of the most prevalent theories is that the administration of President George W. Bush “did” 9/11, or at least knew about it and let it happen because the administration wanted to go to war in Afghanistan and Iraq for oil. Many 9/11 theories branch out of the core conspiracy that 9/11 was an inside job. The “proof”? Supposedly, the Twin Towers could only have collapsed the way they did as a result of controlled demolition (this is false). Another favorite among conspiracy theorists: The Pentagon was not hit by a plane, but by a missile.

A number of prominent figures on the right, including Congresswoman Marjorie Taylor Greene (R-GA), have peddled conspiracy theories about 9/11. According to Slate, InfoWars radio host Alex Jones is “one of the earliest and most influential 9/11 conspiracy theorists” and has helped these ideas gain ground. Just a tip: If you find yourself in a crowd with Greene and Jones, it may be time to rethink a few things.

6. Mass shootings like Sandy Hook were “false flags”

After 20 first-graders and six school staffers were killed at Sandy Hook Elementary School in Connecticut on December 14, 2012, Alex Jones used his formidable platform to claim the attack hadn’t actually happened. The mass shooting, according to Jones, was “completely fake” and the slain children were hired “actors.” Sandy Hook conspiracies spread far and wide, with some grieving parents releasing birth certificates to prove their children existed, and having to deny requests to exhume their children’s bodies. 

Mass shootings continue to bring out the worst in conspiracy theorists. After the Parkland, Florida, shooting at Marjory Stoneman Douglas High School left 17 dead, survivors were called “crisis actors." When a gunman killed 58 people in Las Vegas, theories ran wild that he hadn’t acted alone. And no matter where the shooting takes place or how many people are affected, it seems there are always those who are ready to call it a “false flag” attack, designed by the “deep state” to push gun control laws. But if that were true, don’t you think we would have, you know, passed substantial gun control by now?

7. Top Democrats are behind a child sex ring

In October 2016 (what we used to think of as the most cursed year before we entered the hellscape of 2020), the emails of Hillary Clinton’s campaign chairman, John Podesta, were leaked online. In the emails, Podesta writes about possibly holding a fundraiser at the DC pizzeria Comet Ping Pong, and mentions ordering cheese pizza. These seemingly innocuous details became fuel for the wild conspiracy that Comet Ping Pong was the headquarters of a child sex-trafficking ring run by Democratic leaders, including Clinton and Podesta. Cheese pizza, theorists claimed, actually meant child pornography. As in so many conspiracy communities, the emails became a cipher only insiders could decode.

A few weeks after Podesta’s emails were leaked and “Pizzagate” started gaining traction online, a 28-year-old man walked into the northwest Washington pizzeria with an AR-15 rifle. After his search of the premises yielded no dungeon holding child sex slaves, he fired his gun at a locked door before surrendering to police. 

Although the would-be gunman later told a judge his actions were “foolish and reckless,” Pizzagate conspiracies continued to proliferate online, becoming the seed for the equally fantastical QAnon conspiracy. In October 2017, an anonymous poster called “Q” began posting on the messaging board 4chan, claiming to be an intelligence officer in the U.S. government. Q expanded the foundations of Pizzagate: Not only are politicians and Hollywood elites really satanic pedophiles, they also harvest the blood of children to stay young. The only person who could stop them was Donald Trump. (After the election of President Joe Biden, some in the Q universe continue to insist that Biden is an illegitimate president and Trump is ruling from the shadows, from which he will one day emerge to take power after the arrests of everyone from Hillary Clinton to Tom Hanks to the Pope.)

There’s so much to say about QAnon, including its promoters in Congress (hi again, Marjorie Taylor Greene!), its popularity among suburban mothers, its role in the deadly January 6 insurrection, and its ties to the wellness industry, but we’ll leave you with this: Even Alex Jones appears to have given up on Q.

8. The Earth is actually flat

The 2017 Flat Earth International Conference featured speakers such as Mark Sargent, who runs the Flat Earth Clues YouTube series and has enjoyed a leading role in Netflix’s Behind the Curve, a documentary about Flat Earthers. Sargent claims that the world is a flat soundstage under a dome, sort of like the Truman Show. Although there’s not extensive polling on how many people think the Earth is flat, there’s evidence that younger people are more likely to believe this is the case.

The basic idea of this movement is right there in its name: The Earth is flat, not a globe. Flat Earthers have a range of theories about how they think the world is actually laid out, but the majority seem to believe the planet is a flat disc with an ice wall around it. Although it can be easy to laugh off the Flat Earth theory — which theorists themselves accidentally debunked in Behind the Curve — this kind of belief can be a harbinger of extreme science skepticism about issues with real-world implications, like vaccines.

9. COVID-19 as population control

Conspiracies about the novel coronavirus are a dime a dozen: The vaccine implants a microchip used to track people; the fatality rate has been wildly inflated; oh, and Bill Gates is not only responsible for the virus but also the head of a plot to use the virus as population control. Are you tired yet? I am.

These theories have been debunked repeatedly, yet they persist. That might have something to do with then-president Donald Trump saying the virus was no more deadly than the flu and would one day “disappear, like a miracle” without the need for a vaccine. Or it could be related to some Republican lawmakers who floated the idea that COVID could be a Chinese “bioweapon.” Or it could just be that, in a time of historic political polarization, this country was uniquely ill-suited to deal with a catastrophic pandemic that has killed hundreds of thousands of Americans. Take your pick (and get your vaccine, if you’re able).

Want more from Teen Vogue? Check this out: QAnon Conspiracy Theories Are Driving Families Apart 
