Rafael Sebastián Guillén Vicente is a Mexican insurgent, the former military leader and spokesman for the Zapatista Army of National Liberation (EZLN) in the ongoing Chiapas conflict, and a prominent anti-capitalist and anti-neoliberal. Widely known by his initial nom de guerre Subcomandante Insurgente Marcos, he has subsequently employed several other pseudonyms: he called himself Delegate Zero during the Other Campaign (2006–2007), and since May 2014 has gone by the name Subcomandante Insurgente Galeano, which he adopted in honor of his fallen comrade Jose Luis Solis Lopez, his nom de guerre being Galeano, aka "Teacher Galeano". Marcos bears the title and rank of Subcomandante, as opposed to Comandante, because he is under the command of the indigenous commanders who constitute the EZLN's Clandestine Revolutionary Indigenous Committee's General Command.

The Zapatista Army of National Liberation, often referred to as the Zapatistas, is a far-left political and militant group that controlled a substantial amount of territory in Chiapas, the southernmost state of Mexico.