The Liga Comunista 23 de Septiembre (English: September 23 Communist League), or LC23S, was a Marxist-Leninist urban guerrilla movement that emerged in Mexico in the early 1970s. The result of the fusing of various armed revolutionary organizations active in Mexico prior to 1974 in hopes of creating a united front to combat the Mexican government; the name was chosen to commemorate an unsuccessful guerrilla assault on the barracks in Ciudad Madera in the northern state of Chihuahua led by former schoolteacher Arturo Gámiz and the People's Guerrilla Group on September 23, 1965.
Labeled a terrorist organization by the Mexican authorities, the LC23S engaged in numerous violent attacks that were geared towards eliminating what they believed was a corrupt and authoritarian state that was preventing the popular classes in Mexico from participating in politics and be adequately represented. At that point, the PRI party had held the presidency for more than 40 years since the end of the Mexican Revolution and was, instead of implementing the objectives of the Revolution, reestablishing a largely oligarchic rule of the state. Another objective of the Liga was to eradicate the existing regime and install in its place a socialist state.