Mara Salvatrucha (commonly abbreviated as MS-13) is a transnational criminal gang that originated in Los Angeles and has spread to other parts of the United States, Canada, Mexico, and Central America. The majority of the gang is ethnically composed of Central Americans (mostly Salvadorans) and active in urban and suburban areas. In the U.S., the MS-13 has an especially heavy presence in Los Angeles County and the San Francisco Bay Area in Northern California; the Washington, D.C. metropolitan areas of Fairfax County, Virginia, Montgomery County, Maryland, and Prince George's County, Maryland; Long Island, New York; the Boston, Massachusetts area; Charlotte, North Carolina; and Houston, Texas. There is also a presence of MS-13 in Toronto, Ontario, Canada.

Members of MS distinguish themselves by tattoos covering the body and also often the face, as well as the use of their own sign language. They are notorious for their use of violence and a subcultural moral code that predominantly consists of merciless revenge and cruel retributions. This cruelty of the distinguished members of the "Maras" or "Mareros" earned them a path to be recruited by the Sinaloa Cartel battling against Los Zetas in an ongoing drug war south of the United States border. Their wide-ranging activities have drawn the attention of the FBI and Immigration and Customs Enforcement, who have initiated wide-scale raids against known and suspected gang members – netting hundreds of arrests across the country.