Irrumatio, also called irrumation, is a type of sexual intercourse performed by actively thrusting one's penis into a partner's mouth and throat. It may also be the thrusting of the penis between the legs, feet, upper thighs (also known as interfemoral sex), or between the abdomens of two partners.

"Latin erotic terminology actually distinguishes two acts ... First, fellation, in which the man’s penis is ... orally excited by ... the ... fellatrix ..., [and] Second, irrumation ... in which the man (the irrumator) ... engages in ... motions by moving his hips and body in a rhythm of his own choice."

The English noun irrumatio or irrumation and verb irrumate come from the Latin irrumare, to force one to perform fellatio. Also note that J. L. Butrica, in his review of R. W. Hooper's edition of The Priapus Poems,a co rpus of poems known as Priapeia in Latin, states that "some Roman sexual practices, like irrumatio, lack simple English equivalents."

As the quotation from Butrica suggests, and an article by W. A. Krenkel shows, irrumatio was a widespread sexual practice in the Roman Empire. J. N. Adams states that "it was a standard joke to speak of irrumatio as a means of silencing someone".

Oral sex of any kind was considered to be an act of defilement: the mouth had a particularly defined role as the organ of oratory, as in Greece, to participate in the central public sphere, where discursive powers were of great importance. Thus, to penetrate the mouth could be taken to be a sign of massive power differential within a relationship.

Remaining frescos from the Roman city of Pompeii demonstrate that irrumatio was one of the specific Roman sexual acts, the others being fututio, fellatio, pedicatio and cunnilingus. This was probably because the extant frescos appear to be in bathhouses and brothels: oral sex was something usually practiced with prostitutes because of their lowly status.

Pedicatio and Irrumatio are referenced in Catullus 16. Still, C. A. Williams argues that it was accepted as a degrading act, even more so than anal sex. S. Tarkovsky states that despite being popular, it was thought to be a hostile act, "taken directly from the Greek, whereby the Greek men would have to force the fellatio by violence".

Furthermore as A. Richlin has shown in an article in the Journal of the History of Sexuality it was also accepted as "oral rape", a punitive act against homosexuality. Roman historian Suetonius has a passage in his De Vita Caesarum which inconclusively states that Roman emperor Tiberius took great pleasure from forcing women, even those of rank, to perform fellatio.