Anal sex or anal intercourse is generally the insertion and thrusting of the erect penis into a person's anus, or anus and rectum, for sexual pleasure. Other forms of anal sex include fingering, the use of sex toys for anal penetration, oral sex performed on the anus (anilingus), and pegging. Though the term anal sex most commonly means penile-anal penetration, sources sometimes use the term anal intercourse to refer exclusively to penile-anal penetration, and anal sex to refer to any form of anal sexual activity, especially between pairings as opposed to anal masturbation.
While anal sex is commonly associated with male homosexuality, research shows that not all gay males engage in anal sex and that it is not uncommon in heterosexual relationships. Types of anal sex can also be a part of lesbian sexual practices. People may experience pleasure from anal sex by stimulation of the anal nerve endings, and orgasm may be achieved through anal penetration – by indirect stimulation of the prostate in men, indirect clitoral/G-spot stimulation in women, and associated sensory nerves (especially the pudendal nerve). However, people may also find anal sex painful, sometimes extremely so, which may be primarily due to psychological factors in some cases.
As with most forms of sexual activity, anal sex participants risk contracting sexually transmitted infections (STIs/STDs). Anal sex is considered a high-risk sexual practice because of the vulnerability of the anus and rectum. The anal and rectal tissues are delicate and do not provide natural lubrication, so they can easily tear and permit disease transmission, especially if lubricant is not used. Anal sex without protection of a condom is considered the riskiest form of sexual activity, and therefore health authorities such as the World Health Organization (WHO) recommend safe sex practices for anal sex.