List of serial killers by number of victims
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. There are gaps of time between the killings, which may range from a few days to months, or many years. This list shows serial killers from the 20th century to present day by number of victims. 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. Organization and ranking of serial killings is made difficult by the complex nature of serial killers and incomplete knowledge of the full extent of many killers' crimes. 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. The fourth column in the table states the number of victims definitely assigned to that particular  serial killer, and thus the table is in order of that figure. The fifth column states the number of possible victims the killer could have murdered. Some of these crimes are unsolved, but were included because they are the work of a serial killer, despite nobody being caught. This list does not necessarily include war criminals or members of democidal governments, such as Adolf Hitler, Francisco Franco, Hideki Tojo, Suharto, Mao Zedong, Joseph Stalin, or Pol Pot. Serial killers with the highest known victim count. The most prolific modern serial killer is arguably Dr. Harold Shipman, with 218 probable murders  and possibly as many as 250 (see "Medical professionals", below). However he was actually convicted of a sample of 15 murders. Excluding these "Medical professionals and pseudo-medical professionals", with their ability to kill simply and in plain sight, and Serial killer groups and couples (below), this list is a compilation of modern serial killers currently with the highest verifiable murder count. Serial killers with 15 to 30 victims. This part of the list contains all serial killers with 15 to 30 proven victims who acted alone and were neither medical professionals nor contract killers. Serial killers with 5 to  14 proven victims. This part of the list contains all serial killers with five to fourteen proven victims who acted alone and were neither medical professionals nor contract killers. Serial killers with fewer than five proven victims. This part of the list contains all serial killers with fewer than five proven victims who acted alone and were neither medical professionals nor contract killers. Disputed cases. <nowiki>*</nowiki> "Proven victims" being victims the serial killer was tried for, explained by the killer in a detailed confession, or victims most scholars of the subject agree upon. List of serial killers by