311 may refer to: * 311 (number), a natural number * AD 311, a year of the Julian calendar, in the fourth century AD * 311 BC, a year of the pre-Julian Roman calendar * 311 (band), an American band ** 311 (album), ''311'' (album), band 311's self-titled album * 311 (DSM-IV), DSM-IV code for "Depressive Disorder Not Otherwise Specified" * 311 Boyz, a teen gang in Las Vegas, Nevada * 3-1-1, the telephone number of local information service operated by some local governments in the United States and Canada * 3-1-1 for Carry-Ons, a procedure enacted by the United States Transportation Security Administration * 311 earthquake, the 2011 Tōhoku earthquake and tsunami off Japan * 311, the area code of a common fictitious telephone number (311-555-2368) used in early Bell System ads and in fiction

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