Anders Behring Breivik (born 13 February 1979) is a Norwegian mass murderer, neo-Nazi, and domestic terrorist who perpetrated the 2011 Norway attacks. A believer in the Great Replacement theory, he sought to combat perceived "Cultural Marxism" by detonating a car bomb at the Regjeringskvartalet (executive government quarter) in Oslo, then carrying out a mass shooting at a summer camp of the Labour Party's youth wing on the island of Utøya, in total killing 77 people and injuring over 323.

Found competent to stand trial, Breivik was tried in 2012, convicted on all charges, and sentenced to 21 years of preventive detention, with the possibility of extensions for as long as he is deemed to pose a danger to society.

At age 16, he was arrested for graffiti vandalism in Oslo. He later joined the anti-immigration Progress Party, chaired its Vest Oslo youth branch in 2002, and left in 2006. He joined a gun club in 2005. A company he founded later went bankrupt, and he reported no income in 2009. He financed the attacks with about €130,000 using credit cards.

On the day of the attacks, Breivik distributed a compendium titled 2083: A European Declaration of Independence, outlining his ideology. In it, he opposed Islam, blamed feminism for a perceived European "cultural suicide", and called for the deportation of Muslims from Europe, stating that publicising the text was a primary motive.

Two teams of forensic psychiatrists evaluated Breivik before trial. While the first diagnosed paranoid schizophrenia, a second concluded he was not psychotic at the time of the attacks and instead had narcissistic personality disorder and antisocial personality disorder.

Breivik has since filed multiple legal challenges against the Norwegian Correctional Service under the European Convention on Human Rights regarding his confinement. A partial ruling in his favor in 2016 was overturned on appeal, and later challenges, including a 2024 case on prison isolation, were unsuccessful.

Early life Breivik was born in Oslo on 13 February 1979, the son of Jens Breivik (born 1935), a civil economist, who worked as a diplomat for the Norwegian Embassy in London and later in Paris, and Wenche Elisabeth Behring (1946–2013), a nursing assistant. He has a maternal half-sister named Elisabeth, and three paternal half-siblings: Erik, Jan, and Nina. Breivik lived in London until aged one, when his parents divorced. His family name is Breivik, and his middle name, Behring, is his mother's maiden name. In 2017, it was reported he had changed his legal name to Fjotolf Hansen.

When Breivik was aged four, and living in Oslo's Frogner borough, two reports were filed expressing concern about his mental health. A psychologist in one report made a note of the boy's peculiar smile, suggesting it was not anchored in his emotions but was rather a deliberate response to his environment. In another report from Norway's National Centre for Child and Adolescent Psychiatry (SSBU), concerns were raised about how Breivik was treated by his mother: "[s]he 'sexualised' the young Breivik, hit him, and frequently told him that she wished that he were dead."

In the report, Wenche Behring is described as "a woman with an extremely difficult upbringing, borderline personality disorder and an all-encompassing if only partially visible depression" who "projects her primitive aggressive and sexual fantasies onto [Breivik]". The report recommended he be forcibly removed from his mother and placed into foster care, as she was heavily emotionally and psychologically abusive towards him, but this was not carried out by the Child Welfare Service.– Breivik var skadet allerede som toåring. Retrieved 9 April 2021. "Psykologen ved Statens Senter for Barne – og Ungdomspsykiatri (SSBU), som på 80-tallet observerte samspillet mellom Anders og hans mor, ble avhørt av politiet etter terroraksjonen 22.juli 2011."

Breivik's mother had fled her abusive home at age 17 and soon after that became a teenage mother. In her thirties, she became pregnant with Anders and married his father, Jens Breivik. During her pregnancy, she moved to London, where Jens worked. Even before his birth, Breivik's mother developed a disdain for her son. She claimed that he was a "nasty child" and that he was "kicking her on purpose". She had wanted an abortion, but by the time she went to a hospital, she had passed the three-month threshold. Psychologist reports later stated that she thought that Breivik was a "fundamentally nasty and evil child and determined to destroy her". She stopped breastfeeding her son early on because he was "sucking the life out of her".

A year after Breivik's birth, his parents' relationship ended. Breivik's mother moved back to Oslo, where she borrowed Jens Breivik's apartment in the Frogner borough. Neighbours claimed that there were noises of fights and that the mother left her children alone for extended periods, while she was working as a nurse. In 1981, Breivik's mother applied for financial welfare benefits; in 1982, she applied for respite care for her son. She said that she was overwhelmed with the boy and unable to care for him. She described him as "clingy and demanding". Breivik was then placed, in cooperation with the Child Welfare Service, with a young couple, who later told police that the mother, when bringing two-year-old Breivik to the house, had asked that he be allowed to touch the man's penis because he had no one to compare himself to in terms of appearance; "He has only ever seen girls' parts", the mother told the couple, according to the couple's undated statement to police.– Breivik var skadet allerede som toåring. Retrieved 9 April 2021. Han så bare jentetisser', fortalte hun dem."

In February 1983, on the advice of her neighbours, Breivik's mother sought help from the National Centre for Child and Adolescent Psychiatry (SSBU); Breivik and his mother were outpatients, and they stayed there during the daytime for about one month. The psychiatrists' conclusion of the stay was that Breivik should be placed in the foster care system and had to be removed from his mother for him to develop normally. This was based on several observations: in contrast to the highly demanding child that his mother had described, Breivik actually had little emotional engagement and did not show joy, or cry when he was hurt; he also made no attempts to play with other children, was extremely clean, and became anxious when his toys were not in order. He did not show the normal level of uncleanliness of a four-year-old, and had no repertoire on how to express emotions normally. On rare occasions, his long phases of emotional voidness would be interrupted by fits where he would erupt and display extreme uncontrolled emotions.

Psychologists inferred from this that Breivik was subjected to punishment or extreme negative reactions whenever he displayed emotions, leading him to become outwardly emotionless. They also believed that the boy had developed obsessive–compulsive disorder (OCD) as a result of fear of punishment by his mother, who had claimed to them that he was unclean and that she constantly had to care for him.

Reports of the staff said that his mother had told Breivik that she "wished that he was dead" even in the presence of health personnel. At the same time she bound him emotionally to her, alternating between great affection and extreme cruelty from one moment to the next. Some nights, Breivik and his mother would share the bed with close body contact. The psychiatrists concluded this was an unacceptable situation for a four-year-old to be in and the report from 1983 stated: "Anders is a victim of his mother's projections of paranoid-aggressive and sexual fears toward men in general", and "she projects onto him her own primitive, aggressive and sexual fantasies; all the qualities in men that she regards as dangerous and aggressive". Breivik reacted very negatively to his mother and alternated between clinginess, petty aggression and extreme childishness.

The final conclusion of the observation was that the "family is in dire need of help. Anders should be removed from the family and given a better standard of care; the mother is provoked by him and remains in an ambivalent position which prevents him from developing on his own terms. Anders has become an anxious, passive child that averts making contact. He displays a manic defence mechanism of restless activity and a feigned, deflecting smile. Considering the profoundly pathological relationship between Anders and his mother it is crucial to make an early effort to ward off a severely skewed development in the boy." However, Child Welfare Services did not follow this recommendation, and instead he was placed in respite care only during the weekends.

When Breivik's father learned of the situation, he filed for custody. Although Breivik's mother had agreed to have him put in respite care, after Jens had filed for custody she demanded that Breivik be put back into full custody with her. Both the mother and father involved lawyers and eventually, the case was dropped because the Welfare Services thought that they would not be able to provide enough evidence in court to warrant the placement of Breivik in foster care. One of the main reasons for this was the testimony of staff from the Vigelandsparken Nursery, which Breivik had been attending since 1981, who both described him as a happy child and claimed that nothing was or had been wrong with him all along.

The SSBU, however, maintained their stance regarding Breivik, going so far as to state that "urgent action is crucially needed to prevent a severely skewed development in the boy". The SSBU wrote Child Welfare Services a letter claiming that an order should be placed to have Breivik removed by force. In 1984, a hearing in front of Barnevernsnemnda (the municipal child welfare committee) took place on whether Breivik's mother should lose custody of him. The Child Welfare Service lost the case; the agency was represented by a social worker with no prior experience representing a case in front of the committee. It was ruled only that the family should be supervised; however, after only three visits, even this supervision was discontinued. Breivik was never again put into respite care or foster care.

Later childhood and adolescence Breivik attended Smestad Grammar School, Ris Junior High, and Oslo Commerce School. A former classmate recalled that Breivik was an intelligent student, physically stronger than others of the same age, who often took care of people who were bullied. Breivik resided with his mother and elder half-sister in the West End of Oslo, regularly visiting his father and stepmother, who had now moved to France, until they divorced when he was 12. His mother remarried to an officer in the Norwegian Army. Breivik chose to be confirmed into the Lutheran Church of Norway at the age of 15.

In his adolescence, Breivik's behaviour was described as rebellious. In his early teen years, he was a prolific graffiti artist and part of the hip hop music community in Oslo West. He took his graffiti much more seriously than his associates did, and was caught by the police on several occasions; Child Welfare Services were notified once again and he was fined twice. According to Breivik's mother, his father ceased contact with him at age 16 after his first arrest for spray painting graffiti on private property. According to Breivik's father, however, his son was the one who ended contact, as he claimed, "I was always willing to see [Anders] despite his destructive activities". At this age, Anders fell out with his best friend and broke off contact with the hip-hop community.

Beginning in adolescence, Breivik spent his spare time weight training and started to use anabolic steroids. He focused on his appearance and strength.

Adulthood