ATP is a common abbreviation of All Tomorrow's Parties, primarily a regular music festival, the organisation also runs other live events and the record ATP Recordings record label.

Named after the song "All Tomorrow's Parties" by The Velvet Underground, it was founded by Barry Hogan in 1999 as an alternative to larger, more corporate festivals like Reading or Glastonbury, with a tendency towards post-rock, avant-garde, and underground hip hop, along with more traditional rock fare, but presented in an environment more intimate than a giant stadium or huge country field. ATP is a sponsorship free festival where the organisers and artists stay in the same accommodation as the fans.

The festival has its origins in the Bowlie Weekender, curated by Belle & Sebastian at Camber Sands in April 1999. Artists, usually musicians (but sometimes visual artists like Matt Groening or Jake and Dinos Chapman) are asked to curate the festival by inviting their favourite performers to play. The idea is that it is akin to dipping into the curator's record collection, or as Thurston Moore of Sonic Youth described it, "It's the ultimate mix tape". Steve Albini, a curator in 2002, has been quoted as stating that "There are three things in the world that I endorse: Abbey Road … Nutter Butter Sandwich Cookies; and All Tomorrow's Parties," while Mike Patton stated it was his favourite gig of all time.

In 2002, the festival expanded to the USA, and several events have taken place there in subsequent years. In recent years the ATP organisation has also been involved in booking stages at the Pitchfork Music Festival and the Primavera Sound Festival in Barcelona. In 2008, ATP ran their first East-Coast US. festival, which took place at the Kutshers Country Club, Monticello, New York on September 19-21 and was a huge success. In January 2009, the festival took place for the first time in Australia, with events in Brisbane, Sydney and Mt Buller (in Victoria) all curated by Nick Cave & The Bad Seeds.

The small organisation that puts on these festivals also promote concerts in London and the rest of the United Kingdom, curate the yearly Don't Look Back concert series and run the record label ATP Recordings.