Birth of the Marimacho: Modernismo’s Trans* Cultural Productions in Latin America analyzes the emergence of a new gender expression in early-twentieth-century Latin American literature, science, and visual culture: the ‹‹marimacho››. In the Hispanic tradition, marimacho is the umbrella notion that may refer to a sexist slur as much as a modern form of non-binary gender, a transmasculine identification, or a lesbian identity. This project examines the aesthetic construction of this hybrid, counter-cultural, and gender-dissident figure in an extensive cultural repertoire that includes novels, plays, films, leaflets, medical studies, prison and mental hospital records, poems, and newspaper and tabloid articles. I seek to increase the understanding of the region’s politics of gender and sexuality during the modernizing era (1880s-1930s), that is, before the solidification of LGBTQ activism, pride literature, and minority social movements of the Global 1960s. In response to the new gender dynamics led by cosmopolitan networks of first-wave feminism, the keepers of gender normativity created the marimacho as a monstrous version of conventional masculinity. The main objective of this research is to investigate why a broad range of cultural materials named queer women, non-binary individuals, and trans* men as marimachos, as gender hackers that put at stake the futures of heteronormativity, reproduction, and family life.