Sexual sadism disorder is the condition of experiencing sexual arousal in response to the extreme pain, suffering or humiliation of others. Several other terms have been used to describe the condition, and the condition may overlap with other conditions that involve inflicting pain. It is distinct from situations in which consenting individuals use mild or simulated pain or humiliation for sexual excitement. The words "sadism" and "" are derived from Marquis de Sade.

Biastophilia (from Greek "biastes", "rape" + "-philia") and its Latin language-derived counterpart raptophilia (from Latin "rapere", "to seize"), also paraphilic rape, is a paraphilia in which sexual arousal is dependent on, or is responsive to, the act of assaulting an unconsenting person, especially a stranger. Some dictionaries consider the terms synonymous, while others distinguish raptophilia as the paraphilia in which sexual arousal is responsive to actually raping the victim.

The source of the arousal in these paraphilias is the victim's terrified resistance to the assault, and in this respect it is considered to be a form of sexual sadism. Biastophilia is accepted as potentially lethal, other such paraphilias including, but not being limited to asphyxiophilia, autassassinophilia, hybristophilia, and chremastistophilia.

Under the name paraphilic coercive disorder, this diagnosis was proposed for inclusion in DSM-5. This diagnosis, under the name "paraphilic rapism", was proposed and rejected in the DSM-III-R. It has been criticized because of the impossibility of reliably distinguishing between paraphilic rapists and non-paraphilic rapists, and because this diagnosis, under the term "Paraphilia NOS" (not otherwise specified), non-consent had been used in Sexually Violent Person/Predator commitment.

Czech sexology standardly use a concept of pathologic sexual aggressivity instead. This term is strongly distinguished from sadism. This disorder is understood as a coordination anomaly of the sexual motivation system (SMS), a "courtship disorder" according to Kurt Freund or displacement paraphilia by John Money, or a missing segment of SMS.

Courtship disorder is a theoretical construct in sexology in which a certain set of paraphilias are seen as specific instances of anomalous courtship instincts in men. The specific paraphilias are biastophilia (paraphilic rape), exhibitionism, frotteurism, telephone scatologia, and voyeurism. According to the "courtship disorder hypothesis", there is a species-typical courtship process in human males consisting of four phases, and anomalies in different phases result in one of these paraphilic sexual interests. That is, instead of being independent paraphilias, this theory sees these sexual interests as individual symptoms of a single underlying disorder.

With paraphilic coercive disorder, the individual employs enough force to subdue a victim, but with sexual sadism disorder, the individual often continues to inflict harm regardless of the compliance of the victim, which sometimes escalates not only to the death of the victim, but also to the mutilation of the body. What is experienced by the sadist as sexual does not always appear obviously sexual to non-sadists: Sadistic rapes do not necessarily include penile penetration of the victim. In a survey of offenses, 77% of cases included sexual bondage, 73% included anal rape, 60% included blunt force trauma, 57% included vaginal rape, and 40% included penetration of the victim by a foreign object. Moreover, in 40% of cases, the offender kept a personal item of the victim as a souvenir.

On personality testing, sadistic rapists apprehended by law enforcement have shown elevated traits of impulsivity, hypersexuality, callousness, and psychopathy.

Although there appears to be a continuum of severity from mild ("hyperdominance" or "BDSM") to moderate ("paraphilic coercive disorder") to severe ('sexual sadism disorder), it is not clear if they are genuinely related or only appear related superficially.

Very little is known about how sexual sadism disorder develops. Most of the people diagnosed with sexual sadism disorder come to the attention of authorities by committing sexually motivated crimes. Surveys have also been conducted including people who are interested in only mild and consensual forms of sexual pain/humiliation (BDSM).

Most of the people with full-blown sexual sadism disorder are male, whereas the sex ratio of people interested in BDSM is closer to 2:1 male-to-female.

People with sexual sadism disorder" are at an elevated likelihood of having other paraphilic sexual interests.

According to the "courtship disorder hypothesis", there is a species-typical courtship process in humans consisting of four phases. These phases are: "(1) looking for and appraising potential sexual partners; (2) pretactile interaction with those partners, such as by smiling at and talking to them; (3) tactile interaction with them, such as by embracing or petting; (4) and then sexual intercourse."

The associations between these phases and these paraphilias were first outlined by Kurt Freund, the originator of the theory: A disturbance of the search phase of courtship manifests as voyeurism, a disturbance of the pretactile interaction phase manifests as exhibitionism or telephone scatologia, a disturbance of the tactile interaction phase manifests as toucheurism or frotteurism, and the absence of the courtship behavior phases manifests as paraphilic rape (i.e., biastophilia). According to Freund, these paraphilias "can be conceptualized as a preference for a pattern of behavior or erotic fantasy in which one of these four phases of sexual interaction is intensified and distorted to such an extent that it appears to be a caricature of the normal, while the remaining phases are either omitted entirely or are retained only in a vestigial way."

Freund noted that "troilism" (a paraphilia for observing one’s sexual/romantic partner sexually interacting with a third party, usually unbeknownst to the third party) might also be a courtship disorder, troilism being a variant of voyeurism.

Appropriate behaviors depend on the social and cultural context, including time and place. Some behaviors that are unacceptable under most circumstances, such as public nudity or sexual contact between dancers, may be accepted or even encouraged during celebrations like Carnival or Mardi Gras. Where such cultural festivals alter normative courtship behaviors, the signs of courtship disorder may be masked or altered.

Hybristophilia is a paraphilia in which sexual arousal, facilitation, and attainment of orgasm are responsive to and contingent upon being with a partner known to have committed an outrage, cheating, lying, known infidelities or crime, such as rape, murder, or armed robbery. The term is derived from the Greek word ὑβρίζειν "hubrizein", meaning "to commit an outrage against someone" (ultimately derived from ὕβρις "hubris" "hubris"), and "philo", meaning "having a strong affinity/preference for". In popular culture, this phenomenon is also known as "Bonnie and Clyde Syndrome".

Many high-profile criminals, particularly those who have committed atrocious crimes, receive "fan mail" in prison that is sometimes amorous or sexual, presumably as a result of this phenomenon. In some cases, admirers of these criminals have gone on to marry the object of their affections in prison.

Hybristophilia is accepted as potentially lethal, among other such paraphilias including, but not being limited to, asphyxiophilia, autassassinophilia, biastophilia, and chremastistophilia.

The reason why some people do this is unknown, but some speculations have been offered. For instance, Katherine Ramsland, who is a professor of forensic psychology at DeSales University mentions that some of the women in particular who have married or dated male serial killers have offered the following reasons:

- "Some believe they can change a man as cruel and powerful as a serial killer."

- "Others 'see' the little boy that the killer once was and seek to nurture him."

- "A few hoped to share in the media spotlight or get a book or movie deal."

- "Then there's the notion of the 'perfect boyfriend'. She knows where he is at all times and she knows he's thinking about her. While she can claim that someone loves her, she does not have to endure the day-to-day issues involved in most relationships. There’s no laundry to do, no cooking for him, and no accountability to him. She can keep the fantasy charged up for a long time."

Others offered reasons along the lines of:

- "Some mental health experts have compared infatuation with killers to extreme forms of fanaticism. They view such women as insecure females who cannot find love in normal ways or as 'love-avoidant' females who seek romantic relationships that cannot be consummated."

From a perspective focusing on male serial killers attracting female partners, Leon F. Seltzer (psychologist), has offered explanations based on evolutionary psychology. Serial killers, in his view, are cases of alpha males that tend to attract women. This is because such males were good at protecting women and their offspring in our evolutionary history. Women nowadays may consciously realize that it is unwise to date a serial killer, but they are nevertheless attracted to them, as he notes "as a therapist I've encountered many women who bemoaned their vulnerability toward dominant men who, consciously, they recognized were all wrong for them". As evidence of women's fantasy preference for dominant men, he refers to the book "A Billion Wicked Thoughts: What the World's Largest Experiment Reveals about Human Desire" by Ogi Ogas and Sai Gaddam. Seltzer discusses Ogas and Gaddam's argument that this fantasy is the dominant plot of most erotic/romantic books and movies written for women but the fantasy always holds that this male dominance is conditional, "it doesn't really represent the man's innermost reality".