Paraphilia (previously known as sexual perversion and sexual deviation) is the experience of intense sexual arousal to atypical objects, situations, fantasies, behaviors, or individuals. Such attraction may be labeled sexual fetishism. No consensus has been found for any precise border between unusual sexual interests and paraphilic ones. There is debate over which, if any, of the paraphilias should be listed in diagnostic manuals, such as the "Diagnostic and Statistical Manual of Mental Disorders" (DSM) or the International Classification of Diseases (ICD).

The number and taxonomy of paraphilia is under debate; one source lists as many as 549 types of paraphilia. The DSM-5 has specific listings for eight paraphilic disorders. Several sub-classifications of the paraphilias have been proposed, and some argue that a fully dimensional, spectrum or complaint-oriented approach would better reflect the evidence.

Sexual fetishism or erotic fetishism is a sexual fixation on a nonliving object or nongenital body part. The object of interest is called the fetish; the person who has "a fetish" for that object is a fetishist. A sexual fetish may be regarded as a non-pathological aid to sexual excitement, or as a mental disorder if it causes significant psychosocial distress for the person or has detrimental effects on important areas of their life. Sexual arousal from a particular body part can be further classified as partialism.

While medical definitions restrict the term "sexual fetishism" to objects or body parts, "fetish" can also refer to sexual interest in specific activities in common discourse.

The ICD-10 defines fetishism as a reliance on non-living objects for sexual arousal and satisfaction. It is only considered a disorder when fetishistic activities are the foremost source of sexual satisfaction, and become so compelling or unacceptable as to cause distress or interfere with normal sexual intercourse. The ICD's research guidelines require that the preference persists for at least six months, and is markedly distressing or acted on.

Under the DSM-5, fetishism is sexual arousal from nonliving objects or specific nongenital body parts, excluding clothes used for cross-dressing (as that falls under transvestic disorder) and sex toys that are designed for genital stimulation. In order to be diagnosed as "fetishistic disorder", the arousal must persist for at least six months and cause significant psychosocial distress or impairment in important areas of their life. In the DSM-IV, sexual interest in body parts was distinguished from fetishism under the name partialism (diagnosed as Paraphilia NOS), but it was merged with fetishistic disorder for the DSM-5.

The ReviseF65 project has campaigned for the ICD diagnosis to be abolished completely to avoid stigmatizing fetishists. Sexologist Odd Reiersøl argues that distress associated with fetishism is often caused by shame, and that being subject to diagnosis only exacerbates that. He suggests that, in cases where the individual fails to control harmful behavior, they instead be diagnosed with a personality or impulse control disorder.

Sadomasochism is the giving or receiving pleasure from acts involving the receipt or infliction of pain or humiliation. Practitioners of sadomasochism may seek sexual gratification from their acts. While the terms sadist and masochist refer respectively to one who enjoys giving or receiving pain, practitioners of sadomasochism may switch between activity and passivity.

The abbreviation S&M is often used for sadomasochism, although practitioners themselves normally remove the ampersand and use the acronym S-M or SM or S/M when written throughout the literature. Sadomasochism is not considered a clinical paraphilia unless such practices lead to clinically significant distress or impairment for a diagnosis. Similarly, sexual sadism within the context of mutual consent, generally known under the heading BDSM, is distinguished from non-consensual acts of sexual violence or aggression.

Pedophilia or paedophilia is a psychiatric disorder in which an adult or older adolescent experiences a primary or exclusive sexual attraction to prepubescent children. Although girls typically begin the process of puberty at age 10 or 11, and boys at age 11 or 12, criteria for pedophilia extend the cut-off point for prepubescence to age 13. A person who is diagnosed with pedophilia must be at least 16 years old, and at least five years older than the prepubescent child, for the attraction to be diagnosed as pedophilia.

Pedophilia is termed pedophilic disorder in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5), and the manual defines it as a paraphilia involving intense and recurrent sexual urges towards and fantasies about prepubescent children that have either been acted upon or which cause the person with the attraction distress or interpersonal difficulty. The International Classification of Diseases (ICD-10) defines it as a sexual preference for children of prepubertal or early pubertal age.

In popular usage, the word "pedophilia" is often applied to any sexual interest in children or the act of child sexual abuse. This use conflates the sexual attraction to prepubescent children with the act of child sexual abuse, and fails to distinguish between attraction to prepubescent and pubescent or post-pubescent minors. Researchers recommend that these imprecise uses be avoided because although people who commit child sexual abuse are sometimes pedophiles, child sexual abuse offenders are not pedophiles unless they have a primary or exclusive sexual interest in prepubescent children, and some pedophiles do not molest children.

Pedophilia was first formally recognized and named in the late 19th century. A significant amount of research in the area has taken place since the 1980s. Although mostly documented in men, there are also women who exhibit the disorder, and researchers assume available estimates underrepresent the true number of female pedophiles. No cure for pedophilia has been developed, but there are therapies that can reduce the incidence of a person committing child sexual abuse. The exact causes of pedophilia have not been conclusively established. Some studies of pedophilia in child sex offenders have correlated it with various neurological abnormalities and psychological pathologies. In the United States, following "Kansas v. Hendricks", sex offenders who are diagnosed with certain mental disorders, particularly pedophilia, can be subject to indefinite civil commitment.

Frotteurism is a paraphilic interest in rubbing, usually one's pelvic area or erect penis, against a non-consenting person for sexual pleasure. It may involve touching any part of the body, including the genital area. A person who practices frotteuristic acts is known as a "frotteur". Toucherism is sexual arousal based on grabbing or rubbing one's hands against an unexpecting (and non-consenting) person. It usually involves touching breasts, buttocks or genital areas, often while quickly walking across the victim's path. Some psychologists consider toucherism a manifestation of frotteurism, while others distinguish the two. In clinical medicine, treatment of frotteuristic disorder involves cognitive behavior therapy coupled with the administration of a SSRI.

Zoophilia is a paraphilia involving a sexual fixation on non-human animals. Bestiality is cross-species sexual activity between human and non-human animals. The terms are often used interchangeably, but some researchers make a distinction between the attraction (zoophilia) and the act (bestiality).

Although sex with animals is not outlawed in some countries, in most countries, bestiality is illegal under animal abuse laws or laws dealing with buggery or crimes against nature.

The World Health Organization (WHO) lists ego-dystonic sexual orientation in the ICD-10, as a disorder of sexual development and orientation. The WHO diagnosis covers when gender identity or sexual orientation is clear, yet a patient has another behavioural or psychological disorder which makes that patient want to change it. The diagnostic manual notes that a sexual orientation is not a disorder in itself. The World Health Organization (WHO) notes that any particular sexual orientation (heterosexuality, homosexuality, or bisexuality) is not a mental disorder by and of itself.

Similarly, the American Psychological Association has officially opposed the category of ego-dystonic homosexuality since 1987. In 2007, a task force of the American Psychological Association undertook a thorough review of the existing research on the efficacy of reparative therapy for. Their report noted that there was very little methodologically sound research on sexual orientation change efforts (SOCEs) and that the "results of scientifically valid research indicate that it is unlikely that individuals will be able to reduce same-sex attractions or increase other-sex sexual attractions through SOCE." In addition, the task force found that "there are no methodologically sound studies of recent SOCE that would enable the task force to make a definitive statement about whether or not recent SOCE is safe or harmful and for whom." The diagnostic category of "ego-dystonic homosexuality" was removed from the American Psychiatric Association's DSM in 1987 (with the publication of the DSM-III-R). Sexual disorders are still present in the DSM under the category of "sexual disorder not otherwise specified". One of the disorders under this category is "persistent and marked distress about one’s sexual orientation”, which can be considered similar to what WHO describes as ego-dystonic sexual orientation.

The Medical Council of India uses the WHO classification of ego-dystonic sexual orientation. The "Chinese Classification and Diagnostic Criteria of Mental Disorders" includes ego-dystonic homosexuality.

Males with late onset gender dysphoria "frequently" display transvestic fetishism.

Some male transvestic fetishists collect women's clothing, e.g. panties, nightgowns, babydolls, bridal gowns, slips, brassieres, and other types of nightwear, lingerie, stockings, pantyhose, shoes, and boots, items of a distinct feminine look and feel. They may dress in these feminine garments and take photographs of themselves while living out their fantasies.

According to DSM-IV, this fetishism was limited to heterosexual men; however, DSM-5 does not have this restriction, and opens it to women and men with this interest, regardless of their sexual orientation.

There are two key criteria before a psychiatric diagnosis of "transvestic fetishism" is made:

1. Individuals must be sexually aroused by the act of cross-dressing.

2. Individuals must experience significant distress or impairment – socially or occupationally – because of their behavior.

The word "pedophilia" comes from the ("paîs, paidós"), meaning "child", and φιλία ("philía"), "friendly love" or "friendship". "Pedophilia" is used for individuals with a primary or exclusive sexual interest in prepubescent children aged 13 or younger.

"Infantophilia" is a sub-type of pedophilia; it is used to refer to a sexual preference for children under the age of 5 (especially infants and toddlers). This is sometimes referred to as "nepiophilia" (from the ("népios") meaning "infant" or "child," which in turn derives from "ne-" and "epos" meaning "not speaking"), though this term is rarely used in academic sources. "Hebephilia" is defined as individuals with a primary or exclusive sexual interest in 11- to 14-year-old pubescents. The DSM-5 does not list hebephilia among the diagnoses; while evidence suggests that hebephilia is separate from pedophilia, the ICD-10 includes early pubertal age (an aspect of hebephilia) in its pedophilia definition, covering the physical development overlap between the two philias. In addition to "hebephilia", some clinicians have proposed other categories that are somewhat or completely distinguished from pedophilia; these include "pedohebephilia" (a combination of pedophilia and hebephilia) and "ephebophilia" (though ephebophilia is not considered pathological).

The professional handbook of the American Psychiatric Association (APA), the "Diagnostic and Statistical Manual of Mental Disorders", fifth edition, lists the following diagnostic criteria for "frotteuristic disorder".

- Over a period of at least 6 months, recurrent and intense sexual arousal from touching or rubbing against a nonconsenting person, as manifested by fantasies, urges, or behaviors.

- The individual has acted on these sexual urges with a nonconsenting person, or the sexual urges or fantasies cause clinically significant distress or impairment in social, occupational, or other important areas of functioning.

If the individual has not acted on their interest and experiences no distress or impairment, they are considered to have a frotteuristic sexual interest, but not frotteuristic disorder. Some sexologists distinguish between frotteurism (as pelvic rubbing) and toucherism (as groping with hands), but the DSM does not. Sexologist Kurt Freund described frotteurism and toucherism as courtship disorders that occur at the tactile stage of human courtship.

Ego-dystonic sexual orientation is an ego-dystonic mental disorder characterized by having a sexual orientation or an attraction that is at odds with one's idealized self-image, causing anxiety and a desire to change one's orientation or become more comfortable with one's sexual orientation. It describes not innate sexual orientation itself, but a conflict between the sexual orientation one wishes to have and the sexual orientation one actually possesses.

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.

The DSM-IV-TR describes paraphilias as "recurrent, intense sexually arousing fantasies, sexual urges or behaviors generally involving nonhuman objects, the suffering or humiliation of oneself or one's partner, or children or other nonconsenting persons that occur over a period of six months" (criterion A), which "cause clinically significant distress or impairment in social, occupational, or other important areas of functioning" (criterion B). DSM-IV-TR names eight specific paraphilic disorders (exhibitionism, fetishism, frotteurism, pedophilia, sexual masochism, sexual sadism, voyeurism, and transvestic fetishism, plus a residual category, paraphilia—not otherwise specified). Criterion B differs for exhibitionism, frotteurism, and pedophilia to include acting on these urges, and for sadism, acting on these urges with a nonconsenting person. Sexual arousal in association with objects that were designed for sexual purposes is not diagnosable.

Some paraphilias may interfere with the capacity for sexual activity with consenting adult partners.

In the current version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), a paraphilia is not diagnosable as a psychiatric disorder unless it causes distress to the individual or harm to others.

Some people eroticize about intimate examinations as part of a medical fetish, and as such are a common service offered by professional dominants.

An intimate examination can form part of a scene in medical play where the nurse or doctor inflicts one or more embarrassing and humiliating quasi-medical procedures on the patient. Often frozen or heated objects are introduced to the patient's body to simulate the uncomfortable sensations that can occur during a real examination. Examinations may include an examination and intrusion of the anus, urethra, or vagina, as well as handling and twisting of the penis, testicles, clitoris, and nipples. Quite often, strap on play is also incorporated, as this can heighten the intimacy, and also the sensations of the patient. This may be a prelude to masturbation or administration of an enema. Before examination, the patient can be placed in physical restraints and gagged, and wear some form of embarrassing clothing.

Medical fetishism refers to a number of sexual fetishes involving objects, practices, environments, and situations of a medical or clinical nature. In sexual roleplay a hospital or medical scene involves the sex partners assuming the roles of doctors, nurses, surgeons and patients to act out specific or general medical fetishes. Medical fantasy is a genre in pornography, though the fantasy may not necessarily involve pornography or sexual activity.

Medical fetishism may involve sexual attraction to respiratory therapy involving oxygen via nasal cannula or any sort of masks, medical practitioners, medical uniforms, hospital gowns, anaesthesia, intimate examinations (such as rectal examination, gynecological examination, urological examination, andrological examination, rectal temperature-taking), catheterization, diapering, enemas, injections, insertion (such as suppository insertion, menstrual-cup insertion, and prostatic massage), medical devices (such as orthopedic casts and orthopedic braces; see also "Abasiophilia"), dental objects (such as dental braces, retainers, and headgear), medical restraints, and medical gags.

Spectrophilia is sexual attraction to ghosts or sexual arousal from images in mirrors, as well as the phenomenon of sexual encounters between ghosts and humans.

HSDD was listed under the Sexual and Gender Identity Disorders of the DSM-IV. In the DSM-5, it was split into male hypoactive sexual desire disorder and female sexual interest/arousal disorder. It was first included in the DSM-III under the name inhibited sexual desire disorder, but the name was changed in the DSM-III-R. Other terms used to describe the phenomenon include sexual aversion and sexual apathy. More informal or colloquial terms are "frigidity" and "frigidness".

In the DSM-5 all paraphilia disorders can be diagnosed by two main criteria that are referred to criteria A and criteria B respectively. The A and B criteria include a duration in which the behavior must be present for (typically 6 months) and specific details of actions or thoughts that are correlated specifically with the respective disorder being diagnosed.

Spectrophilia is a fetish that is classified as the paraphilia in which one is attracted to ghosts or spirits. Spectrophiliacs fantasize about ghosts and often imagine scenarios involving sexual events between themselves or others and spirits.

Transvestic fetishism is a psychiatric diagnosis applied to those who are thought to have an excessive sexual or erotic interest in cross-dressing; this interest is often expressed in autoerotic behavior. It differs from cross-dressing for entertainment or other purposes that do not involve sexual arousal, and is categorized as a paraphilia in the Diagnostic and Statistical Manual of the American Psychiatric Association. (Sexual arousal in response to donning sex-typical clothing is homeovestism.)

Hand fetishism or hand partialism or also Quirofilia is the sexual fetish for hands. This may include the sexual attraction to a specific area such as the fingers, palm or nails, or the attraction to a specific action performed by the hands; which may otherwise be considered non-sexual—such as washing or drying dishes. This fetish may manifest itself as a desire to experience physical interaction, or as a source of sexual fantasy.

Hand fetishism is recognized by the porn industry; however, it is one of the least common fetishes, despite foot fetishism being the most common.

Hand fetishism is usually based in the biological indication that a partner is healthy and a good potential mate.

Voyeurism is the sexual interest in or practice of spying on people engaged in intimate behaviors, such as undressing, sexual activity, or other actions usually considered to be of a private nature.

The term comes from the French "voir" which means "to see". A male voyeur is commonly labeled as "Peeping Tom" or a "Jags", a term which originates from the Lady Godiva legend. However, that term is usually applied to a male who observes somebody secretly and, generally, not in a public place.

Hypoactive sexual desire disorder (HSDD) or inhibited sexual desire (ISD) is considered a sexual dysfunction and is characterized as a lack or absence of sexual fantasies and desire for sexual activity, as judged by a clinician. For this to be regarded as a disorder, it must cause marked distress or interpersonal difficulties and not be better accounted for by another mental disorder, a drug (legal or illegal), some other medical condition, or asexuality. A person with ISD will not start, or respond to their partner's desire for, sexual activity.

There are various subtypes. HSDD can be general (general lack of sexual desire) or situational (still has sexual desire, but lacks sexual desire for current partner), and it can be acquired (HSDD started after a period of normal sexual functioning) or lifelong (the person has always had no/low sexual desire.)

HSDD has garnered much criticism, primarily by asexual activists. They point out that HSDD puts asexuality in the same position homosexuality was from 1974-1987. The DSM at that time recognised 'ego-dystonic homosexuality' as a disorder, defined as sexual interest in the same sex that caused significant distress. The DSM itself officially recognized this as unnecessarily pathologizing homosexuality and removed it as a disorder in 1987.

Gerontophilia is the sexual preference for the elderly. A person with such a sexual preference is a gerontophile. The word "gerontophilia" was coined in 1901 by Richard von Krafft-Ebing. It derives from Greek: geron, meaning "old man or woman" and philie, meaning "love". Gerontophilia is classified as a paraphilia, but is not mentioned in the "Diagnostic and Statistical Manual of Mental Disorders" or International Classification of Diseases.

The prevalence of gerontophilia is unknown. A study of pornographic search terms on a peer-to-peer network reported that 0.15% had gerontophilic themes. Sex offenders with elderly victims do not necessarily have gerontophilia. There are other possible motivations for these offenses, such as rage or sadism, or the increased vulnerability of elderly as a social group, which are factors that may not involve a sexual preference for the elderly. There are no studies showing that most such offenders are gerontophiles. In one small study, two of six sex offenders against the elderly evinced gerontophilic tendencies. Gerontophilia can also be expressed with consenting elderly partners in a legal context.

Research on gerontophilia is limited to a small number of case studies, beginning with a paper by French physician Charles Féré in 1905. Féré described a 27-year-old man who rejected an arranged marriage with a 20-year-old "beauty" in favor of a 62-year-old woman. Such studies commonly report that the subject had an early sexual experience with a much older woman.