Rape by gender

This article classifies types of rape by the sex of both the rapist and the victim. The scope of the article includes both rape and sexual violence more generally.

Since only a small percentage of acts of sexual violence are brought to the attention of the authorities, it is impossible to compile accurate statistics. There are nevertheless statistical estimates published by some official bodies. The U.S. Bureau of Justice Statistics (1999) estimated that 91% of United States rape victims were female and 9% were male, with 99% of the offenders being male and 1% of the offenders being female. Several studies argue that male-male and female-female prison rape are quite common and may be the least reported form of rape.

Rape of females by males
In a 2000 research article from the Home Office, in England and Wales around 1 in 20 women (4.9%) said that they had been raped at some point in their life from the age of 16 beyond.

A woman's physiological response to sexual contact is involuntary. In some cases, women can become physically aroused, produce natural lubrication, and even experience orgasms against their will during rape.

Pregnancy may result from rape. The rate varies between settings and depends particularly on the extent to which non-barrier contraceptives are being used. A study of adolescents in Ethiopia found that among those who reported being raped, 17% became pregnant after the rape, a figure which is similar to the 15–18% reported by rape crisis centres in Mexico. A longitudinal study in the United States of over 4000 women followed for 3 years found that the national rape related pregnancy rate was 5.0% per rape among victims aged 12–45 years, producing over 32 000 pregnancies nationally among women from rape each year. Experience of coerced sex at an early age reduces a woman’s ability to see her sexuality as something over which she has control.

Rape of males by males
Several studies argue that male-male prisoner rape might be the most common and least-reported form of rape, with some studies suggesting such rapes are substantially more common in both per-capita and raw-number totals than male-female rapes in the general population.

Research from the UK suggests that almost 3% of men reported a non-consensual sexual experience as adults and over 5% of men reported sexual abuse as a child. This does not take into account the possibility of exaggeration or false reports nor of underreporting. Recognition of male on male rape in law has historically been limited; the first successful prosecution for attempted male on male rape in the UK was not until 1995.

Male on male rape has historically been shrouded in secrecy due to the stigma men associate with being raped by other men. According to psychologist Dr Sarah Crome fewer than one in ten male-male rapes are reported. As a group, male rape victims reported a lack of services and support, and legal systems are often ill equipped to deal with this type of crime.

Rape of males by females
Contrary to popular opinion, women also can commit an act of rape with force or deception to make a man engage in a non-consensual penetrative sexual act. However, due to social double standards, reports are rarely taken seriously, if made at all. According to "Court TV"'s "Crime Library", women commit about 2% of all sexual offenses and their abuse often involves their own child or children, but this statistic doesn't mention how many, if any, of these cases of abuse were rape.

Statutory female-on-male rape
Several widely publicized cases of female-on-male statutory rape in the United States involved school teachers raping their underage students. (See e.g. Mary Kay Letourneau)

Non-statutory female-on-male rape
Much like female erectile response and contrary to popular opinion, male erectile response is involuntary, meaning that a man need not consent mentally or physically for his penis to become erect and be placed in a woman's vagina. Penetration of a man by a woman is possible through use of a strap-on or other object. Rape of a man by a woman could also occur when limited sexual activities are agreed upon and a man's penis is placed in a woman in violation of the limits that had been set. Rape of a man by a woman is thus possible in several ways.

However, male victims of sexual abuse by females often face social, political, and legal double standards. Though some  studies show otherwise, female abusers are usually seen as less culpable than male abusers/rapists by the courts due to these misconceptions. Since rape by females is much less well known than male-female abuse, male victims of female abusers often find little support from rape crisis centers and even the authorities. While gender neutral laws have combated the older perception that rape never occurs to men, and other laws have eliminated the term altogether, the double standards still remain. Due to these reasons, it is likely being substantially under-reported, with the probable cause being the double standard.

As with female-on-male rape, pregnancy can result, with the victim legally bound to pay child support to his rapist.

Rape of females by females
Female on female rape is often labeled "lesbian rape", though the sexual identity of one or both (or more) persons involved may or may not actually be lesbian. Forced penetration by another female is possible with the use of strap-ons, dildos, other foreign objects and digital penetration.

A few books, such as Violent Betrayal: Partner Abuse in Lesbian Relationships by Dr. Claire M. Renzetti, No More Secrets: Violence in Lesbian Relationships by Janice Ristock, and Woman-to-Woman Sexual Violence: Does She Call It Rape? by Lori B. Girshick also cover the topic of rape of females by other females.