Mountain was an American rock band formed on Long Island, New York, in 1969. Originally consisting of vocalist-guitarist Leslie West, bassist-vocalist Felix Pappalardi, keyboardist Steve Knight, and drummer N. D. Smart (soon replaced by Corky Laing), the group disbanded in 1972, but reunited on several occasions prior to West's death in 2020. They are best known for their 1970 smash hit song "Mississippi Queen", which remains a staple of classic rock radio, as well as the heavily sampled song "Long Red", and their performance at Woodstock Festival in 1969. Mountain is one of many bands commonly credited with influencing the development of heavy metal music during the 1970s. The group's musical style primarily consisted of hard rock, blues rock, and heavy metal.

The beginning of the live recording of their song "Long Red" has become one of the most sampled drum breaks in hip hop, sampled in over 700 songs by artists such as EPMD, Pete Rock & CL Smooth, A Tribe Called Quest, Nas, Kanye West, the Game, among many others. Songs using the sample include Jay-Z's "99 Problems" and Kanye West's "The Glory".

In early 1969 Leslie West, formerly of the Long Island R&B band The Vagrants, put together a band, Leslie West Mountain, with Norman Landsberg (keyboards, bass) and Ken Janick (drums) and began playing gigs and recording demos. Right around this time, former Cream collaborator/producer Felix Pappalardi, who had previously produced the Vagrants, expressed an interest in producing West's work. West, previously disgruntled and unsatisfied with the lack of success in his first project, found Cream to be a great inspiration. He began to feel disillusioned with the R&B and blues scenes of the 1960s in which he had played. He envisioned a project that would take on a rawer and much harder style which he had begun to favor, with his newly developed guitar style inspired by hearing Cream's Eric Clapton.

Pappalardi rejected the demos by the West-Landsberg-Janick trio, but took a suggestion that he play bass on West's solo album, Mountain. The album also featured Landsberg and former Remains drummer N.D. Smart. The album spotlighted West's raw vocals and melodic, bluesy guitar style, and Pappalardi's bass lines were prominent. According to West, when Pappalardi asked what would be next, West suggested the pair go on the road. Keyboardist Steve Knight (from Devil's Anvil, another of Pappalardi's productions) was added after Landsberg left to form another group, Hammer, with Janick.

Naming themselves "Mountain", after West's 1969 solo album, West, Pappalardi, Smart, and Knight played shows on the west coast before getting to play their third concert as a working band at the 1969 Woodstock Festival in Bethel, New York. Mountain was received enthusiastically by the festival audience but the band did not appear in the film of the event, nor was their performance included on volume 1 of the festival's live album. Their performances of "Blood of the Sun" (from West's album) and "Theme for an Imaginary Western" (a song they planned to record for Climbing! and written by former Cream bassist Jack Bruce) appeared on the second volume of Woodstock performances, "Woodstock II", although neither of those "live" songs were recorded at Woodstock. The 40th Anniversary Edition of Woodstock on DVD and Blu-ray features filmed performances of "Beside The Sea" and "Southbound Train".

Soon after Woodstock, Smart was replaced by Canadian Laurence "Corky" Laing, who was the drummer on Climbing!, which was released in March 1970. It led off with what became the band's signature song, "Mississippi Queen", which reached No. 21 in the Billboard Hot 100, and was featured in the 1971 cult film Vanishing Point, while the album reached No. 17. Laing wrote most of the song spontaneously when his previous band, Energy, was playing a show and the power went out. Because his drums were acoustic Laing continued to play for over an hour to keep the audience dancing, namely an attractive Southern woman who was dancing in the emergency lights. He shouted out some of the lyrics, "Mississippi Queen, do you know what I mean?", accompanied with his signature cowbell the iconic track would later be known for.

Mountain began a hectic touring schedule in the middle of which they recorded a follow-up album, Nantucket Sleighride, released in January 1971. This album reached No. 16 but failed to yield a hit single. The title track was used in the UK as the theme to ITV's Sunday political program Weekend World. After these early releases the band continued to receive a certain measure of critical acclaim but never again achieved great commercial success.

After Nantucket Sleighride, the band produced Flowers of Evil (November 1971) consisting of one side of studio material and one live side, culled from a concert at New York's Fillmore East.