The foco theory of revolution by way of guerrilla warfare, also known as foquismo (Spanish: [foˈkismo]), was formulated by French intellectual and government official Régis Debray, whose main source of inspiration was Marxist revolutionary Che Guevara's experiences surrounding his rebel army's victory in the 1959 Cuban Revolution.

Che Guevara (left), whose plan was to use the communist zone on the western shores of Lake Tanganyika as a training ground for the Congolese and fighters from other revolutionary communist movements

Its central principle is that vanguardism by cadres of small, fast-moving paramilitary groups can provide a focus (in Spanish foco) for popular discontent against a sitting regime and thereby lead a general rebellion. Although the original approach was to mobilize and launch attacks from rural areas, many foco ideas were adapted into urban guerrilla warfare movements by the late 1960s.