*Various theories regarding President [[John F. Kennedy]]'s assassination. There are a number of theories proposed here, generally along the lines that the assassination was not conducted by [[Lee Harvey Oswald]] acting alone, but was part of some larger murder conspiracy. This may be the first of the modern conspiracy theories. (Similarly, theories exist that his son, John F. Kennedy Jr., did not die in the plane crash which killed him, his wife, and sister-in-law.)
*Denial of the [[Shroud of Turin]] implicitly requires a farfetched conspiracy theory, that someone severely injured, bloodied and allowed himself to be scourged so that co-conspirators would then promote a fake shroud despite not making any money from it.
*[[Apollo conspiracy theory]]: The theory that the [[Apollo 11]] lunar landing on July 20, 1969, and indeed the entire Apollo program, was fake. Supporters analyze photographs and often claim that satellite photographs of [[Area 51]] resemble a movie studio. This view is common among those who hold to the [[flat Earth]] theory.
*Various [[9/11 conspiracy theories]]. People who embrace these are called [[Truther]]s. The theories generally state that the World Trade Center buildings were not brought down by airplane collisions, but (typically) by detonation of explosives planted earlier.<ref>They claim that Jewish workers had been telephoned in advance and told not to come to work (false), that airplane collisions would have caused the buildings to topple over rather than collapse directly downward (false, ignorant of high-school physics), or that the heat of burning aviation fuel would not raise the temperature sufficiently to melt the girders (false, the temperature to make iron visibly bend is much higher than the temperature to make it lose the strength needed to hold up a building, in addition the buildings had other materials inside (both in their construction, as well as items typically found in office settings such as paper) which would increase the temperatures).</ref> Truthers often ascribe the motivation for this to some kind of nefarious scheme by the [[George W. Bush]] administration. Among the websites promoting these theories are [[Infowars]] and [https://wearechange.org We Are Change].
*The belief that President [[Franklin D. Roosevelt]] knew about the [[Attack on Pearl Harbor]] in advance, and allowed it to happen, so America could get into the war; that officers ignored evidence that the attack had started.<ref>From decrypts of Japanese communications, American intelligence expected a major military operation within that time frame, but believed it would take place in southern Asia.</ref>