Phish is an American rock (rock music) band noted for its musical improvisation, extended jams (jam session), exploration of music across genres and devoted fan base. Formed at the University of Vermont in 1983, the bands four members performed together for over 20 years until an official breakup in August 2004. The band reunited in 2009 for three shows at the Hampton Coliseum in USCityHamptonVirginia, and have resumed their former activities with a full summer, a fall tour, a new album titled Joy (Joy (Phish album)), their eighth festival (Phish festivals#Festival 8) in Indio, California, and four shows in Miami, Florida, culminating on New Years Eve.

Their music blends elements of a wide variety of genres, including rock (rock music), jazz, progressive rock, psychedelic rock, funk, bluegrass (bluegrass music), reggae, country (country music), blues, avant garde, and classical (classical music). Each of their concerts is original in terms of the songs performed, the order in which they appear and the way in which they are performed.

Although the band has received little radio play or mainstream exposure, it has developed a large and dedicated following by word of mouth, the exchange of live recordings and selling over 8 million albums and DVDs in the United States. Rolling Stone stated that the band helped to "...spawn a new wave of bands oriented around group improvisation and superextended groove (groove (music))s."