In my dissertation, I examine Mexican detective fiction of the twentieth and twenty-first centuries written by Mexican feminist writers whose literary works include Mexican female detective characters. Writers and works I analyze in this dissertation are María Elvira Bermúdez's "Detente, sombra," (1962) and "Las cosas hablan" (1985) in conjunction with Bermúdez's socio-historical study, La vida familiar del mexicano (1955), argenmex writer Myriam Laurini's Morena en rojo (1994), and Patricia Valldares' Tan frío como el infierno (2014). All three writers challenge previous criticism that had relegated the genre to low-art, entertainment literature and redefine the social and literary roles writers of detective fiction play in Mexican social history through the lenses of decolonial feminism, legal-storytelling, and hemispheric studies. In Chapter One, I examine the evolution of the detective genre beginning with founding father Edgar Allen Poe, moving eastward into Europe with the inclusion of Sir Arthur Conan Doyle and Agatha Christie, I then head towards the Américas, with the U.S. hard-boiled novel and Latin America's novela negra, that places the genre as a tool for social critique and I further discuss the presence of detective, crime, and mystery fiction in Mexico. In Chapter Two, I discuss María Elvira Bermúdez's legacy as one of the first women in twentieth-century Mexico to earn a university degree, attend law school, and become a Supreme Court judge while she simultaneously and passionately dedicated herself to writing and critiquing detective fiction. In Chapter Three, I underscore the value argenmex writer Myriam Laurini brings to the genre with her itinerant Afro-Mexican detective, la Morena. The narrative serves as an ethnographic narrative on Mexican women's issues involving race, class, gender, sexuality, and citizenship. Chapter Four introduces Patricia Valladares' first novel, Tan frío como el infierno taking place in post-modern twenty-first century Mexico City with the radical feminist detective Milena Ruiz who traces the social histories and geographies of women's bodies as "territorios de guerra." Chapter Five discusses what happens to crime fiction in the hands of Mexican feminist writers, women who as writer-activists forge their professional and creative lives within the wider context of the history of Mexican feminism.