The National Liberation Army is a Marxist–Leninist guerrilla insurgency group involved in the continuing Colombian conflict, which has existed in Colombia since 1964. The ELN advocates a composite communist ideology of Marxism-Leninism and liberation theology. In 2013, it was estimated that the ELN forces consisted of between 1,380 and 3,000 guerrillas. According to former ELN national directorate member Felipe Torres, one fifth of ELN supporters have taken up arms. The ELN has been classified as a terrorist organization by the governments of Colombia, the United States, Canada, New Zealand, and the European Union.

The Colombian conflict began on May 27, 1964, and is a low-intensity asymmetric war between the government of Colombia, far-right paramilitary groups and crime syndicates, and far-left guerrilla groups, fighting each other to increase their influence in Colombian territory. Some of the most important international contributors to the Colombian conflict include multinational corporations, the United States, Cuba, and the drug trafficking industry.