The Private Case is a collection of erotica and pornography held initially by the British Museum and then, from 1973, by the British Library. The collection began between 1836 and 1870 and grew from the receipt of books from legal deposit, from the acquisition of bequests and, in some cases, from requests made to the police following their seizures of obscene material.

Henry Spencer Ashbee was a book collector, writer and bibliographer. He is notable for his massive, clandestine three-volume bibliography of erotic literature published under the pseudonym of Pisanus Fraxi.