The study of French science fiction - even in France - remains an underexploited field. Only recently have French literary scholars been able to gain recognition for the validity of studying SF, but their works are often literary histories. This is the first book-length study to take into account both French and Anglo-American intellectual trends, theories, and SF scholarship and apply them to a corpus of French works. It shows how contemporary French SF imagines two broad philosophical inquiries into the powerful, yet terrifying geological age of the Anthropocene: posthumanism and transhumanism. While the posthumanist perspective calls attention to the interdependence and co-evolution of humans and nonhumans within a complex ecosystem of life, the transhumanist view of coping with the Anthropocene offers more pragmatic, tool-based solutions, rather than a reworking of the human imagination. Given the history of philosophical thought's entanglement with literature in France, French SF can tell us a lot about this existential crisis of Anthropos as both destroyer and savior of worlds and bodies alike. With a focus on encounters between humans, nonhumans, and posthumans in selected works, this book investigates both the immaterial (the psychological state of the mind) and material (the body) stakes of posthumanist or transhumanist thinking in French SF.