Ghosts I–IV is the sixth studio album by the American industrial rock band Nine Inch Nails, released by The Null Corporation on March 2, 2008.

The production team included Nine Inch Nails frontman Trent Reznor, studio collaborators Atticus Ross and Alan Moulder, and contributions from Alessandro Cortini, Adrian Belew, and Brian Viglione.

Reznor described Ghosts as "a soundtrack for daydreams," a sentiment echoed by critics, who compared it to the work of Brian Eno and Robert Fripp.

The album was released under a Creative Commons license (BY-NC-SA) and in a variety of differing packages and prices, including a $300 deluxe edition, without prior announcement.

"[5] Reznor explained, "I've been considering and wanting to make this kind of record for years, but by its very nature it wouldn't have made sense until this point".

Live-band member Alessandro Cortini and studio musicians Adrian Belew and Brian Viglione also contributed instrumental performances on select tracks.

"[9] Viglione's makeshift drum kit included a 50-gallon trash can, a pair of water cooler jugs, and a cookie tray with a chain across it.

"[12] PopMatters' review of the album compared its musical style to that of Brian Eno and Robert Fripp, ultimately categorizing it as "dark ambient".

[15] Ghosts I–IV features a wide assortment of musical instruments, including piano, guitar, bass, synthesizer, marimba, tambourine, banjo, dulcimer, and xylophone, many of which were sampled and distorted electronically.

[17] Ghosts I–IV was released online on March 2, 2008, on the official Nine Inch Nails website in a number of different formats at various price points.

[23][24] Reznor explained this move by saying "It's a stance we're taking that we feel is appropriate [...] with digital technology, and outdated copyright laws, and all the nonsense that's going on these days".

[25] Jim Guerinot, then manager of Nine Inch Nails, explained the unconventional release of the album as "[not] a reaction to what doesn’t exist today.

[29][30] Reznor explained that the endeavor was not meant as a contest, but as "an experiment in collaboration and a chance for us to interact beyond the typical one-way artist-to-fan relationship.

[32] Ghosts I–IV material was implemented into Nine Inch Nails live performances typically as a distinct section of instrumental songs midway through the show.

[35] The Ghosts section was later scrapped for the "NINJA" and "Wave Goodbye" tours, as Reznor felt the instrumental songs did not fit with the set lists.

[36] Seth Colter Walls of Newsweek described the album as "the kind of absorbing musical experience that the surviving ranks of know-it-all record-store clerks would be pushing on customers, if only they could offer it for sale.

The review went on to describe each track as "the sonic equivalent of a silver orb hovering in your living room [which then] explodes into a million shiny balls of mercury that splash to the floor before trickling, magnetically, back into a large round mass.

"[45] The album's unorthodox distribution methods also garnered the attention of various news agencies, such as Wired's Eliot Van Buskirk, who labeled Ghosts as "a remarkably extensive release.

"[49] In its review of The Slip, however, PopMatters described Ghosts I–IV in retrospect as an "aimless batch of... instrumentals packaged in a brilliant marketing scheme" and said that it was "basically a CD release with a couple of mail-order special editions available for the 'true fans'.

[53] Rolling Stone magazine named Reznor number 46 in its "100 People Who Are Changing America" list, concluding that he has "been more creative than anyone in embracing the post-CD era".

[28] A week after the album's release, the official Nine Inch Nails site reported over 780,000 purchase and download transactions, amassing over $1.6 million in sales.

[66] "34 Ghosts IV" was sampled by music producer YoungKio for a beat subsequently used on the 2018 Lil Nas X song "Old Town Road," with Reznor's and Ross' writing credits.