A memory hole is any mechanism for the alteration or disappearance of inconvenient or embarrassing documents, photographs, transcripts, or other records, such as from a web site or other archive, particularly as part of an attempt to give the impression that something never happened. The concept was first popularized by George Orwell's dystopian novel Nineteen Eighty-Four.
In the walls of the cubicle there were three orifices. To the right of the speakwrite, a small pneumatic tube for written messages, to the left, a larger one for newspapers; and in the side wall, within easy reach of Winston's arm, a large oblong slit protected by a wire grating. This last was for the disposal of waste paper. Similar slits existed in thousands or tens of thousands throughout the building, not only in every room but at short intervals in every corridor. For some reason they were nicknamed memory holes. When one knew that any document was due for destruction, or even when one saw a scrap of waste paper lying about, it was an automatic action to lift the flap of the nearest memory hole and drop it in, whereupon it would be whirled away on a current of warm air to the enormous furnaces which were hidden somewhere in the recesses of the building.
In the novel, the memory hole is a slot into which government officials deposit politically inconvenient documents and records to be destroyed. Nineteen Eighty-Four's protagonist Winston Smith, who works in the Ministry of Truth, is routinely assigned the task of revising old newspaper articles in order to serve the propaganda interests of the government.
For example, if the government had pledged that the chocolate ration would not fall below the current 30 grams per week, but in fact the ration is reduced to 20 grams per week, the historical record (for example, an article from a back issue of the Times newspaper) is revised to contain an announcement that a reduction to 20 grams might soon prove necessary, or that the ration, then 15 grams, would soon be increased to that number. The original copies of the historical record are deposited into the memory hole.
A document placed in the memory hole is supposedly transported to an incinerator from which "not even the ash remains". However, as with almost all claims made by the Party in this novel, the truth is left ambiguous and the reader is not told whether the documents are truly destroyed. For example, a photograph which Winston throws into one early in the novel is produced later during his torture session by O'Brien, who then throws it back, moments later denying having any memory that the event had even occurred. This draws a direct parallel with the Party's general philosophy of doublethink, of which the memory hole is in a sense the physical embodiment; as the novel describes it, "to forget, whatever it was necessary to forget, then to draw it back into memory again at the moment when it was needed, and then promptly to forget it again".
See also 
- George Orwell, Nineteen Eighty-Four, first published by Martin Secker & Warburg, London, 1949. This reference, Penguin Books pocket edition, 1954.