311 (pronounced "three eleven") is an American rock band from Omaha, Nebraska. The band was formed in 1988 by vocalist and guitarist Nick Hexum, lead guitarist Jim Watson, bassist Aaron "P-Nut" Wills, and drummer Chad Sexton. Watson was replaced by Tim Mahoney in 1990. In 1992, Doug "SA" Martinez joined as a second vocalist and turntablist.

311 has released 13 studio albums, two live albums, four compilation albums, four EPs and four DVDs. After a series of independent releases, 311 was signed to Capricorn Records in 1992 and released the albums Music (1993) and Grassroots (1994) to moderate success. They achieved greater success with their 1995 triple platinum self-titled album, which reached number 12 on the Billboard 200 on the strength of the singles "Down" and "All Mixed Up", the former of which topped the Billboard Hot Modern Rock Tracks in 1996. The band's next three albums—Transistor (1997), Soundsystem (1999), and From Chaos (2001)—were also successful, with the first going platinum and the last two going gold. Their 2004 compilation album Greatest Hits '93–'03 was also certified platinum. The band's most recent studio album is 2019's Voyager. As of 2022, 311 has sold over 10 million records in the United States.

The band's name was chosen by Wills from the police code for indecent exposure in Omaha after a friend of the band was arrested and cited for skinny dipping in a public pool.