Resumen: Luis Buñuel was one of the most important filmmakers of Spain. His religious education was really essential in his life, although his doubts about God began when he was young, religiosity has been an influence all along his work and life. Later, when he arrived to Mexico, he started reading Benito Pérez Galdós’ novels, although when he studied at the Students Residence in Madrid he didn’t like his work. He adapted the novels Nazarín and Tristana, and he wrote Viridiana, an original script full of Galdós’ influences from the novels Halma and Ángel Guerra. We will analize the similarities and differences between this films and the novels besides the iconography and influences of the religion.