Mara Salvatrucha, popularly known as MS-13, is an international criminal gang that originated in Los Angeles, California, in the 1970s and 1980s. The gang later spread to many parts of the continental United States, Canada, Mexico, and Central America, and is active in urban, suburban, and rural areas. Most members are Central American, Salvadorans in particular. MS-13 is defined by its cruelty, and rivalry with the 18th Street Gang. As an international gang, its history is closely tied to U.S.–El Salvador relations.
In 2018, the gang accounted for less than 1 percent (10,000) of total gang members in the United States (1.4 million), and a similar share of gang murders. The gang is a core component to Republican Party messaging on immigration policy in the United States. The Trump administration and Republican politicians have argued that hardline immigration policies are necessary to combat MS-13, and have for example justified the Trump administration's implementation of a family separation policy to deal with MS-13. There is no evidence that weak immigration enforcement or sanctuary city policies contribute to MS-13 activity. Republican politicians, President Trump in particular, have falsely accused Democratic politicians of supporting MS-13.