A serial killer is typically a person who murders three or more people, in two or more separate events over a period of time, for primarily psychological reasons.
In many cases, the exact number of victims assigned to a serial killer is not known, and even if that person is convicted of a few, there can be the possibility that they killed many more.
To address this, multiple categories have been provided in order to more accurately describe the nature of certain serial murders.
This is not a reflection of an individual's overall rank, which may or may not vary depending on personal opinion concerning the nature and circumstances of their crimes.
This list does not include mass murderers, spree killers, war criminals, members of democidal governments, or major political figures, such as Adolf Hitler, Francisco Franco, Hideki Tojo, Suharto, Mao Zedong, Joseph Stalin, or Pol Pot.