Montoneros was an Argentine guerrilla organisation active between 1970 and 1979. Its objectives were based on the idea of destabilising the Argentine state and overthrowing the authoritarian governments which lasted from 1966 to 1973. They also sought the return of Perón and the implementation of the Peronist model. In an environment of dictatorship and political violence, the Montoneros opted for the use of urban guerrilla tactics linked to terrorist actions typical of an irregular struggle, which became important in the second half of the 1960s in several Latin American countries. Based on all of the above, this chapter will cover both the violent beginnings of the organisation and the specific and adaptive ideological elements that accompanied Montoneros until its end, not forgetting the influences and exchanges they had with other revolutionary organisations.