A vomitorium is a passage situated below or behind a tier of seats in an amphitheatre or a stadium, through which big crowds can exit rapidly at the end of a performance. They can also be pathways for actors to enter and leave stage. The Latin word vomitorium, plural vomitoria, derives from the verb vomeo, vomere, vomitum, "to spew forth." In ancient Roman architecture, vomitoria were designed to provide rapid egress for large crowds at amphitheatres and stadiums, as they do in modern sports stadiums and large theatres.

The Oregon Shakespeare Festival, for instance, has vomitoria in two of its theatres, the outdoor Elizabethan Stage and the Angus Bowmer Theatre. The voms, as they are called, allow actors to mount the stage from halls cut into the amphitheatre.

There is a common misconception that ancient Romans designated spaces called vomitoria for the purpose of actual vomiting, as part of a binge and purge cycle. According to Cicero, Julius Caesar escaped an assassination attempt because he felt ill after dinner. Instead of going to the latrine, where his assassins were waiting, he went to his bedroom and avoided assassination. This may be the origin of the misconception. The term vomitorium does not appear until the 4th century AD, about 400 years after Caesar and Cicero.

Other sources say that Aldous Huxley was the first to use the misinterpretation in his book Antic Hay in 1923, in the sentence: There strode in, like a Goth into the elegant marble vomitorium of Petronius Arbiter, a haggard and dishevelled person