Avec cette thèse nous prétendons, à travers quelques textes de la culture historique portugaise et du roman portugais, montrer la présence de la confrontation entre les deux régimes de l'imaginaire (diurne et nocturne) décrits par Gilbert Durand dans son œuvre Les structures anthropologiques de l'imaginaire. Nous avons alors vérifié qu'à chacun de ces deux régimes correspond un imaginaire précis. Ainsi, chacun des deux imaginaires que nous avons identifiés regroupe des schémas, des archétypes et des symboles de l'un des deux régimes durandiens. Nous avons nommé l'imaginaire qui regroupe des schémas, des archétypes et des symboles du régime diurne « imaginaire du héros individuel » tandis que l'imaginaire qui regroupe des schémas, des archétypes et des symboles du régime nocturne a été qualifié d' « imaginaire du protagoniste collectif ».L'imaginaire du héros individuel est un imaginaire dans lequel le peuple, les masses, se soumettent à l'autorité d'un chef (d'un guide) héroïsé, acceptant la destinée comme une fatalité de l'aventure humaine. A l'inverse, nous considérons que l'imaginaire du protagoniste collectif est un imaginaire qui inverse les schémas et archétypes typiques du régime diurne, en valorisant la féminité et les profondeurs intimes de l'homme dans une attitude dialectique où les masses, se rebellant contre leurs oppresseurs, s'assument comme le sujet historique par excellence. Un nouveau sujet-héros est ainsi née, non plus individuel, mais collectif.Nous considérons ainsi que dans l'Histoire comme dans la Littérature nous trouvons le conflit majeur entre deux imaginaires qui s'opposent. En 1383-1385 et lors des deux Révolutions du XXe siècle (instauration de la République, en 1910, et Révolution des Œillets, en 1974), le héros individuel est supplanté par le protagoniste collectif. Le Roi solaire de Durand n'est plus le dirigeant de la nation puisque le peuple s'assume comme le protagoniste de l'Histoire. L'imaginaire dominé par le mythe sébastianiste et impérialiste, défendu au XVIIe siècle par António Vieira, n'est plus l'imaginaire prédominant, étant donné que l'imaginaire du protagoniste collectif va finalement s'affirmer collectivement / The aim of this thesis is, through some texts of Portuguese historical culture and from Portuguese novel, to confront the two regimes of the imaginarium (diurnal and nocturnal) described by Gilbert Durant in his work Les structures anthropologiques de l'imaginaire. So, we have verified,, that to each one of the two regimes corresponds oneprecise imaginarium, that is to say, each one of the two imaginaria that we identified assembles schemes, archetypes and symbols of one of the two durandian regimes. We called the imaginarium that assembles schemes, archetypes and symbols of the diurnal regime Imaginaryium of Individual Hero, while the imaginarium that assembles schemes, archetypes and symbols of the nocturnal regime was called Imaginarium of the Collective Protagonist.In the imaginarium of the individual hero the People, the masses, are subjugated to the authority of a leader (guide) looked up as a hero, therefore accepting the destiny as a fatality of the human adventure. We considered, on the contrary, that the imaginarium of the collective protagonist reverses the diurnal regime schemes and typical archetypes, valorizing feminity and the intimate depths of Mankind in a dialectical attitude in which the masses, rebelling against their oppressors, assume themselves as the historical subject. A new hero-subject is (re)born, not individually anymore, but collectively.The novels studied by José Cardoso Pires (Balada da Praia dos Cães and AlexandraAlpha), by José Saramago (Levantado do Chão), by Mário Ventura (Vida e Morte dosSantiago) and by Lídia Jorge (O Dia dos Prodígios) allowed us to confirm the mythological deconstruction of the Portuguese dictatorial period (1926-1974) by these authors. This way we are literally revealed the reality of the oppression and the violence as well as the imaginarium (virile, imperial and heroic) that underlines that reality.The colonial empire - parallel to a situation of unlimited exploitation in the colonies and in Portugal - is attacked in its archetypism, blooming the April Revolution as an imagistic counterpoint to a regime based on the exploitation, fear, violence, oppression, and imposing of submission. The characters depicted in the five novels studied go through the dictatorial years (only the characters of Balada da Praia dos Cães are not acquainted with the Carnation Revolution) to, finally, get in touch with a New World that is born with the 25th of April of 1974.We considered that, both in Literature and in History, we can find the conflict -major between two opposing imaginaria. In 1383-1385 at the time of the two XX century-Revolutions (Instauration of the Republic in 1910, and the April Revolution in 1974), the individual hero is overshadowed by the collective hero. The durandian Solar King is no longer the ruler of a nation, as the people assume themselves as the protagonist of the History. This way the imaginarium controlled by the sebastianist and imperial myth, defended in the XVII century by the priest António Vieira, ceases to be predominant and the collective struggle carried on by the People as the major-protagonist of the History affirms itself imagistically