Valleys of Neptune is a posthumous compilation album by the American rock musician Jimi Hendrix. Released in the United States on March 9, 2010, the album was promoted as having "12 previously unreleased studio recordings", including the title track, "one of the most sought after of all of Hendrix's commercially unavailable recordings"; and as including "the original Jimi Hendrix Experience's final studio recordings".

The tracks on Valleys of Neptune were largely self-produced by Hendrix, and received extra posthumous production from Janie Hendrix, Eddie Kramer and John McDermott. Recorded mostly in 1969 following the release of Electric Ladyland, the album predominantly features the original line-up of the Jimi Hendrix Experience: vocalist and guitarist Hendrix, bass guitarist Noel Redding and drummer Mitch Mitchell. The lead single released from the album was "Valleys of Neptune", on February 1, 2010, followed by "Bleeding Heart" on March 1; music videos were produced for both songs.

The majority of the tracks on Valleys of Neptune were recorded in early 1969, while Hendrix was experimenting with songs for his unfinished fourth album, following the successful release of Electric Ladyland in September 1968.

By the time Valleys of Neptune was released, numerous versions of its tracks had already been released, both officially and otherwise, including the majority of the "previously unreleased" recordings, albeit sometimes in inferior quality or different versions. For example, the original recording of "Trash Man" is here on Valleys of Neptune; a version of "Trash Man" had been released on the 1975 album Midnight Lightning, but truncated at beginning and end, and with Mitchell's and Redding's drums and bass guitar removed and replaced by that of session musicians.

The album artwork is based on a painting by Hendrix himself in 1957. "He went through a phase doing watercolors at school and this was one of the 110 drawings of his that our father kept. When I saw this one he did in 1957, it screamed 'Valleys of Neptune' to me so we knew we'd use it for this project," said his step-sister, Janie. The album artwork is a mix of his painting and a Linda McCartney photograph of him with a blue tint.

Valleys of Neptune received generally positive reviews from critics. At Metacritic, which assigns a normalized rating out of 100 to reviews from mainstream publications, it received an average score of 68, based on 15 reviews. In Rolling Stone, critic Will Hermes found the music beautiful and exciting, while writing, "Are these tracks 'finished' as Hendrix would've intended? Probably not. But as a glimpse of the guitarist extending his reach beyond the Experience trio, it's thrilling.". Greg Kot, writing for the Chicago Tribune, called it "a sharp snapshot of a musical genius in the studio during a period of transition". Ludovic Hunter-Tilney from the Financial Times called the album "a cut above the many posthumous cash-ins released in [Hendrix's] name."

In the Los Angeles Times, Ann Powers was less enthusiastic and felt "fans will be fascinated by these bluesy riffs with the Experience, but this album of unreleased material from the archives doesn't convey much that was unknown." Q found it "lighter sonically" than Hendrix's better known work and ultimately of "limited appeal".

All tracks are written by Jimi Hendrix, except where noted.