Las fuerzas extrañas (Spanish for: The Strange Forces) is a collection of short stories by Argentine writer Leopoldo Lugones, first published in 1906. Despite having been Lugones' least successful work at that time, it is considered to be a key pioneer in the development of the science fiction and fantasy genres in Argentina. The stories all deal with the concept of toying beyond the limits of human knowledge, having most a tendency to develop from a scientist’s invitation of a friend in order to share with them the results of their experiments, resulting, ultimately, in disaster.