AbstractThe concept of the human beast is assigned to the French novelist, Émile Zola, who is the first to codify principles of Naturalism, against which all future naturalist works would be compared. In his novels, especially in the saga Les Rougon-Macquart, the human beast, «la bête humaine», appears as a literary character embedded in the lower social strata, who, due to harsh working and living conditions in the French capital during the Second Empire, acts according to its most basic instincts. The actions of a human beast are violent and brutal and its behavior conditioned by limited education. In his novels, Zola applies the doctrines of biological determinism as well as the laws of heredity attained from scientific readings that were very popular among the intellectuals of the period. However, the theoretical principles recollected in Le roman expérimental (G. Charpentier et Cie Éditeurs, 1880) were not equally applied in other countries due to different literary precedents as well as diverse socio-historical and philosophical backgrounds. This paper aims to examine the nuances in the aesthetic representation of the human beast in Zola’s L’Assommoir (1877), Galdós’ La Desheredada (1881) and Crane’s Maggie, a Girl of the Streets (1843), delving into the behavioral patterns which shape the unique characteristics of their human beasts.