Acquaintance rape is rape that is perpetrated by a person who knows the victim. Examples of acquaintances include someone the victim is dating, a classmate, co-worker, employer, family member, spouse, counselor, therapist, religious official, or medical doctor. Acquaintance rape includes a subcategory of incidents labeled date rape that involves people who are in romantic or sexual relationships with each other. When a rape is perpetrated by a college student on another student, the term campus rape is sometimes used.

Most rapes are perpetrated by a person known to the victim, but acquaintance rape is less likely to be reported than stranger rape. Thus, crime statistics often underestimate the prevalence of acquaintance rape compared to national surveys. The legal consequences of acquaintance rape are generally the same as for stranger rape, except in jurisdictions where marital rape is legal.

Studies distinguishing between stranger rape and those by a person known to the victim go back to the 1950s, when a study examining American police rape files from 1958 and 1960 found about half were alleged to have been committed by men who knew their victims. The phrase acquaintance rape was first used in print in 1982 by feminist writer and activist Diana Russell. She used it as an umbrella term to cover all rapes involving people who know one another, in her write-up of a study of 930 women in San Francisco in which she found that 35% reported having experienced rape or attempted rape by an acquaintance, compared with 11% who reported being raped by strangers. In 1988 American feminist writer Robin Warshaw published I Never Called It Rape, the first major book on acquaintance rape.

Most rape is committed by someone the victim knows. In the United States, the Rape, Abuse & Incest National Network (RAINN) has reported that 45 percent of sexual assaults are committed by an acquaintance and an additional 25 percent by a current or former intimate partner.

A 2004–05 study of 30 predominantly European countries by the United Nations Research Institute found about half of rape victims knew their rapists, over a third by name. 17% were a colleague or boss, 16% a close friend, 11% a former partner, and 7% a current partner. In a major 2009 European Commission study of rape cases across Europe, it was found that 67% of rapists were known to the victim, with most being a current or former partner. In Europe, the most common rape location is in the home of the victim or rapist.

In the U.S., acquaintance rape frequently takes the form of date rape or gang rape. A 1987 survey of 7,000 students at 25 schools found that one in four had been a victim of rape or attempted rape, and 84% of those knew their attacker. The same study found that 16% of male students who admitted rape, and 10% who admitted attempting it, said they had not been acting alone. In 1985 the Association of American Colleges published a report describing what were then called "trains", in which multiple male students rape a woman who is incapacitated by drugs or alcohol. In a survey of 24 documented cases of alleged college gang rapes reported in the 1980s, 13 were perpetrated by fraternity members, nine by groups of athletes, and two by men unaffiliated with a formal group. In a U.S. National Women's Study, 20% of rapists were described as friends, 16% as husbands, 14% as boyfriends, and 9% non-relatives such as handymen, coworkers and neighbours.

A 1992 study of reported rapes in inner-city and suburban Johannesburg, South Africa found 80% of rapes of adult women were perpetrated by strangers, often by men who abducted them at gunpoint on their way to work or broke into their houses. However, the majority of rapes of girls under 16 years of age were perpetrated by people known to them, usually family or friends, and sometimes gang members.

In India, anti-rape campaigns tend to focus on "custodial rape": that is, rape of a woman by a man in a custodial position with higher status than hers, such as a landlord, policeman, or employer.