When people think of serial killers, certain names immediately come to mind: Ted Bundy, Jeffrey Dahmer, John Wayne Gacy, and Jack the Ripper.
But the history of serial murder is far larger—and stranger—than the most famous cases suggest.
Some killers operated for years before authorities understood what was happening. Others were overshadowed by more notorious criminals. Some victims disappeared without receiving much media attention, while disputed evidence and sensational reporting later made it difficult to separate documented facts from legend.
The following 15 serial killers are not necessarily unknown. Several have become notorious within true-crime circles. But compared with the household names of serial-killer history, their stories remain surprisingly unfamiliar.
From a killer who deliberately disappeared after a cross-country murder spree to a woman who may have lured prospective husbands to a deadly Indiana farm, these are 15 serial killers you’ve probably never heard of.
1. Israel Keyes
Israel Keyes is one of the most unsettling serial killers on this list because of how deliberately he attempted to conceal his crimes.
Unlike many serial killers who develop recognizable patterns, Keyes went to extraordinary lengths to avoid creating one.
Born in Utah in 1978, Keyes traveled extensively throughout the United States. He committed his known murders in different locations and often made significant efforts to separate his crimes geographically from his home life.
Investigators eventually linked him to the 2012 murder of coffee-shop owner Samantha Koenig in Anchorage, Alaska.
What made the case particularly disturbing was what investigators discovered about Keyes's preparation.
He had reportedly created hidden caches containing weapons, cash, and other supplies that he could use during future crimes. These so-called "kill kits" had been buried in different locations years before some of his murders.
Keyes also admitted to committing other murders, but he deliberately refused to provide investigators with a complete accounting of his victims.
That means the full extent of his crimes may never be known.
Why Israel Keyes Is So Disturbing
Keyes wasn't simply relying on opportunity. He planned for future crimes years in advance.
His apparent willingness to travel hundreds or thousands of miles, use different methods, and avoid leaving obvious connections between victims makes his case particularly difficult to understand.
Keyes ultimately died by suicide in jail in 2012 before investigators could fully determine how many people he had killed.
2. Clementine Barnabet
Clementine Barnabet is one of the more mysterious names in American true crime.
In the early 1900s, a series of brutal murders occurred in Louisiana and Texas involving entire families. Barnabet eventually became connected to the crimes after investigators claimed she confessed to participating in multiple killings.
The case, however, is surrounded by uncertainty.
Barnabet was associated with a group known as the "Voodoo Murders" by contemporary newspapers, although modern historians have questioned many of the sensational claims surrounding the case.
She was ultimately convicted of murder and sentenced to life imprisonment.
But exactly how many murders she committed—and whether she was responsible for all the killings attributed to her—remains difficult to establish.
The Clementine Barnabet Mystery
Part of what makes Barnabet fascinating is the gap between the historical record and the sensational newspaper coverage of the period.
Some accounts attributed dozens of murders to her, while other evidence suggests a much smaller number.
Her case demonstrates one of the biggest challenges in researching historical serial killers: sometimes the legend becomes more famous than the evidence.
3. Belle Gunness
Belle Gunness may be one of the most fascinating forgotten serial killers in American history.
Born in Norway in 1859, Gunness immigrated to the United States in 1881. She eventually settled in La Porte, Indiana, where she acquired a farm and began attracting men through matrimonial advertisements.
The advertisements promised companionship and potentially a shared future with a financially secure woman.
For some of the men who answered, the journey to Gunness's farm appears to have been their last.
Several prospective suitors disappeared after traveling to Indiana. Investigators later uncovered human remains on Gunness's property, including the remains of people believed to have disappeared after coming into contact with her.
The exact number of victims remains uncertain. At least a dozen victims were identified in connection with the farm, while estimates have ranged considerably higher.
The Belle Gunness Farm
Gunness's story became even more mysterious in April 1908.
A fire destroyed her farmhouse. Investigators discovered the bodies of her children and a decapitated woman's body that was initially identified as Gunness.
But doubts soon emerged.
The body did not appear to match Gunness's known physical characteristics, and her head was never found. Investigators subsequently uncovered additional human remains on the property.
Gunness was never conclusively located after the fire.
Whether she died in the fire or escaped and assumed another identity remains one of the enduring mysteries surrounding her case.
Why Belle Gunness Matters
Gunness represents a particularly unusual type of historical serial killer: someone who appears to have combined financial fraud, manipulation, and murder.
Her use of matrimonial advertisements also makes her case an early example of how seemingly ordinary social opportunities could be turned into deadly traps.
4. Anatoly Slivko
Anatoly Slivko was a Soviet serial killer whose crimes remained hidden for years.
Born in 1938, Slivko worked as a teacher and youth-group leader in the Soviet Union.
That public role gave him access to boys who trusted him.
Slivko's crimes began in the 1960s and continued for years. He targeted boys, often luring them with promises of activities involving his youth organization.
He photographed some of his victims and maintained disturbing records of his crimes.
His eventual arrest in 1985 came after investigators discovered evidence connecting him to multiple murders.
Slivko confessed to killing seven boys, although investigators examined whether he might have been responsible for additional crimes.
The Disturbing Double Life of Anatoly Slivko
What makes Slivko particularly disturbing is the contrast between his public image and his private crimes.
To the community, he was an educator and youth leader.
Behind that respectable image was a murderer who carefully documented his crimes.
His case is a chilling example of how serial offenders can sometimes hide behind positions of trust.
5. Leonarda Cianciulli
Leonarda Cianciulli, sometimes called the "Soap-Maker of Correggio," is one of the strangest female serial killers in European history.
Born in Italy in 1893, Cianciulli became convinced that her family was threatened by supernatural forces.
She reportedly believed that sacrifices were necessary to protect her surviving children.
Between 1939 and 1940, three women disappeared after coming into contact with Cianciulli.
According to the evidence presented at her trial, she murdered the women and attempted to dispose of their remains in bizarre ways.
The case became particularly notorious because Cianciulli claimed that she used the victims' bodies to make soap and cakes.
Some of the details surrounding those claims have become difficult to separate from the historical record and later retellings.
The "Soap-Maker" Legend
Cianciulli's story has become one of the most recognizable examples of a female serial killer whose crimes became intertwined with bizarre folklore.
Her motives, beliefs, and methods make her case dramatically different from many other serial murderers.
She was convicted of three murders and sentenced to 30 years in prison.
Cianciulli died in 1970.
6. Pedro Alonso López
Pedro Alonso López is one of the most notorious serial killers in South American history, yet his name remains relatively unfamiliar to many English-speaking audiences.
Known as the "Monster of the Andes," López was a Colombian serial killer whose crimes primarily involved young girls.
He was arrested in Ecuador in 1980 after being linked to the disappearance and murder of a young girl.
López eventually confessed to a large number of murders.
Investigators uncovered numerous graves connected to his confessions, although the precise number of victims remains difficult to establish.
Why Pedro Alonso López Is So Notorious
López's case spans multiple countries and illustrates the enormous challenges investigators faced when dealing with crimes committed across national borders.
He was convicted in Ecuador and later released after serving part of his sentence.
His subsequent whereabouts have remained uncertain, contributing to the disturbing mythology surrounding his case.
7. Jane Toppan
Jane Toppan was an American nurse who turned her medical knowledge into a weapon.
Born Honora Kelley in 1857, she eventually adopted the name Jane Toppan and worked as a nurse in Massachusetts.
Her victims were often people she encountered through nursing and personal relationships.
Toppan later confessed to numerous poisonings and claimed an extraordinarily high number of murders.
However, investigators could not verify all of her claims.
She was convicted of murdering her foster sister, Elizabeth Brigham, in 1901.
Toppan was found not guilty by reason of insanity and spent the rest of her life in psychiatric institutions.
The Nurse Who Poisoned Her Patients
Toppan's case is particularly disturbing because nursing gave her access to vulnerable people and provided an environment in which unexplained deaths could initially appear natural.
Her story also highlights the difficulty of determining the true victim count of historical serial killers.
Some of the numbers associated with Toppan come from her own statements rather than independently verified cases.
8. Herbert Mullin
Herbert Mullin is one of the most unusual serial killers in American history.
During the early 1970s, Mullin murdered people in California while believing that his actions could somehow prevent a catastrophic earthquake.
His crimes were deeply connected to his increasingly distorted beliefs.
Mullin killed people of different ages and backgrounds, including strangers and people he knew.
His victims were not connected by a conventional criminal motive such as robbery or revenge.
Instead, Mullin believed that killing people was somehow necessary to prevent disaster.
The Santa Cruz Serial Killer
Mullin's murder spree lasted only a relatively short period, but it resulted in numerous deaths.
He was arrested in 1973 after a murder in Santa Cruz County.
Mullin was later convicted of multiple murders and sentenced to life imprisonment.
His case remains particularly disturbing because the murders were apparently driven by beliefs that bore little relationship to reality.
9. Joachim Kroll
Joachim Kroll was a German serial killer whose crimes stretched across several decades.
Born in 1933, Kroll lived a relatively ordinary life on the surface and worked various jobs, including employment in an industrial setting.
Beginning in the 1950s, he murdered women and children in western Germany.
Kroll often targeted victims who were vulnerable and sometimes attacked people he encountered by chance.
His crimes continued for years before authorities finally connected him to multiple murders.
How Joachim Kroll Was Caught
Kroll was arrested in 1976 after the disappearance of a young girl led investigators to his apartment building.
A search of his residence uncovered evidence connecting him to the murder.
Kroll eventually confessed to numerous killings, although investigators were unable to independently verify every confession.
He was convicted of multiple murders and sentenced to life imprisonment.
Kroll died in prison in 1991.
10. The Harpe Brothers
Micajah "Big" Harpe and Wiley "Little" Harpe are among the earliest American criminals sometimes described as serial killers.
Operating in the late 1700s, the Harpes traveled through the frontier regions of Kentucky, Tennessee, and surrounding areas.
They were notorious for robbery and extreme violence.
Unlike many modern serial killers, the Harpes lived in a world where recordkeeping was inconsistent and law enforcement was limited.
As a result, determining exactly how many people they killed is difficult.
Historical accounts attribute numerous murders to the brothers, but some stories became increasingly exaggerated as their reputation grew.
America's Frontier Serial Killers?
Calling the Harpes "serial killers" requires some historical context.
The modern term did not exist during their lifetime, and their crimes occurred in a frontier environment where violent crime was common.
Nevertheless, their repeated killings across different locations fit many modern descriptions of serial murder.
Their story is therefore less a conventional serial-killer case and more a disturbing window into violence on the early American frontier.
11. Charles Cullen
Charles Cullen was a nurse who became one of the most prolific known serial killers in American history.
For years, Cullen worked in hospitals and medical facilities across New Jersey and Pennsylvania.
His victims were primarily patients.
Cullen used medications to kill patients, often exploiting his access to drugs and his position as a healthcare worker.
The true number of his victims remains uncertain because investigators could not independently confirm every killing he claimed.
He eventually confessed to dozens of murders.
How Charles Cullen Was Caught
Cullen's crimes might have continued for much longer if hospital staff had not begun noticing suspicious patterns.
Investigators eventually connected him to unusual patient deaths and medication irregularities.
In 2003, Cullen was arrested.
He later pleaded guilty to numerous murders and attempted murders and received multiple life sentences without the possibility of parole.
His case led to widespread questions about how hospitals handled warnings about dangerous employees.
Potential standalone topic: Charles Cullen: The Killer Nurse Who Murdered His Patients
12. Elizabeth Báthory
Elizabeth Báthory is one of the most famous names on this list—but surprisingly few people know how much of her story remains disputed.
The Hungarian noblewoman lived during the late 16th and early 17th centuries.
According to later accounts, Báthory tortured and murdered large numbers of young women.
The most sensational version of the story claims that she bathed in their blood to preserve her youth.
That detail has become one of the most enduring elements of her legend.
But historians have questioned the accuracy of many of the stories surrounding Báthory.
How Many People Did Elizabeth Báthory Kill?
Numbers ranging from dozens to hundreds have been attributed to Báthory.
However, the enormous victim counts frequently repeated online should not automatically be treated as established fact.
Báthory was never given a conventional public trial. Instead, she was confined to her castle, where she died in 1614.
The historical debate surrounding her case makes her especially interesting.
Was she responsible for a large-scale campaign of murder? Was the extent of her crimes exaggerated? Or did political and financial motives influence the accusations against her?
The surviving evidence has left historians debating the answers for centuries.
13. Carl Panzram
Carl Panzram was a violent criminal who openly embraced his hatred of humanity.
Born in 1891, Panzram spent much of his life moving between states, committing theft, burglary, assault, and murder.
He was repeatedly imprisoned and escaped from custody multiple times.
Panzram later claimed responsibility for numerous murders and other violent crimes.
Not every claim could be independently verified.
But the crimes that were established were already extensive enough to make him one of the most violent criminals of his era.
The Confessions of Carl Panzram
Panzram wrote extensively about his life and crimes while imprisoned.
His writings are among the most disturbing first-person accounts associated with an American serial killer.
Rather than attempting to portray himself as misunderstood or innocent, Panzram frequently expressed extreme contempt for other people and for society itself.
In 1930, Panzram was executed at Leavenworth Penitentiary for murdering a prison employee.
Potential standalone topic: Carl Panzram: The Serial Killer Who Wrote About His Own Crimes
14. Tamara Samsonova
Tamara Samsonova became known internationally after Russian investigators connected her to multiple murders.
Born in 1947, Samsonova lived in St. Petersburg.
She was arrested in 2015 after being linked to the murder and dismemberment of an elderly woman.
Investigators subsequently examined evidence connecting Samsonova to other disappearances and murders.
Russian media gave her the nickname "The Granny Ripper."
Some of the most sensational claims about her alleged victim count remain disputed, making it important to distinguish confirmed evidence from speculation.
The Diary of Tamara Samsonova
One of the strangest aspects of the case involved Samsonova's diary.
Investigators reportedly found handwritten entries describing aspects of her activities.
The discovery created an unsettling picture of a woman who appeared to document parts of her life in writing.
Samsonova was declared mentally incompetent to stand trial and was sent to a psychiatric institution.
Her case remains one of the more unusual examples of a suspected female serial killer emerging in the 21st century.
15. H. H. Holmes
H. H. Holmes is one of the most famous serial killers on this list, but much of what people think they know about him is based on decades of sensationalized storytelling.
Born Herman Webster Mudgett in 1861, Holmes became a con artist, swindler, bigamist, and murderer.
He eventually operated a building in Chicago that later became known as the "Murder Castle."
Newspapers claimed the building had been specifically designed with secret passages, gas lines, trapdoors, and elaborate mechanisms intended to murder unsuspecting visitors.
Some of those stories were exaggerated or invented by sensational newspapers.
What is much less disputed is that Holmes was a prolific fraudster who was convicted of murdering Benjamin Pitezel in 1895.
Investigators subsequently connected Holmes to additional deaths.
How Many Victims Did H. H. Holmes Have?
The popular legend claims that Holmes murdered 27, 100, or even 200 people.
But many of the names on the original lists were later found to be alive, and the actual number of victims remains uncertain.
Holmes himself confessed to numerous murders, but his statements were inconsistent and sometimes clearly self-serving.
He was eventually convicted of Pitezel's murder and executed in 1896.
The Truth About the Murder Castle
The real story of Holmes is arguably more interesting than the myth.
He was a skilled con artist who manipulated people, committed fraud, changed identities, and exploited the rapid growth of Chicago.
The "Murder Castle" legend helped turn him into a cultural icon, but the surviving evidence suggests that the popular version of his story should be treated carefully.
Why Are These Serial Killers So Little Known?
The most famous serial killers tend to dominate popular culture, but notoriety does not necessarily correspond to the number of victims or the historical significance of a case.
Some killers operated before modern forensic science existed.
Others committed crimes across multiple jurisdictions, making them difficult to connect to one another.
In some cases, investigators never established the full victim count.
And with historical cases, sensational newspapers often transformed real crimes into legends that became increasingly difficult to separate from documented evidence.
That's especially true for figures such as Elizabeth Báthory, H. H. Holmes, Clementine Barnabet, and Belle Gunness.
Their stories have been retold so many times that distinguishing what is known, what is suspected, and what is simply legend can be just as fascinating as the crimes themselves.
The Forgotten Side of Serial Killer History
The names that dominate true crime represent only a fraction of the people who have committed multiple murders throughout history.
Some of the killers on this list were eventually caught. Others died before they could be fully investigated. And in several cases, investigators may never know exactly how many victims were involved.
That's what makes lesser-known serial killer cases so compelling.
They often contain unanswered questions that the most famous cases don't.
Who else did they kill?
How many victims were never identified?
What evidence was lost?
And how much of the story that has been passed down is actually true?
Those questions make the forgotten cases of serial murder worth examining—not simply for their shock value, but because they reveal how difficult it can be to reconstruct the truth from incomplete evidence, conflicting testimony, and decades of sensational reporting.
If you want to explore more disturbing cases, check out FrightFuel's other true-crime stories and lists, where we dig into notorious killers, forgotten murder cases, bizarre crimes, and the darker corners of history.
