Contemporary ecofiction, as an emerging genre in world literature, seeks to redefine the place of the human being within the complex web of life through eight fundamental axes: the climate crisis and the narrative of the Anthropocene; the centrality of nature and non-human agency; slow violence and environmental justice; eco-horror and ecological destruction; indigenous ecological knowledge and biotic resistance; ecological hope and reconstructive futures (solarpunk); animals as moral subjects and interspecies empathy; and new materialism and object-oriented ontology. On the other hand, the existentialist philosophy of Jean-Paul Sartre, by reducing nature to the realm of the "in-itself" (en-soi)—a dense, indivisible, ahistorical entity devoid of any meaning or agency—renders any dialogue, dialectic, or empathy with nature impossible. Adopting a comparative approach, this article first reconstructs Sartre's view of nature and then demonstrates how Ibn Tufayl's philosophical-fictional treatise Hayy ibn Yaqzan (6th century AH / 12th century CE) presents a proto-eco-fiction narrative in which nature appears as an active character, a moral teacher, and a necessary condition for self-awareness. The findings indicate that while Sartre posits nature as an alien and neutral entity standing against the free human project, Ibn Tufayl portrays a kind, generous nature endowed with epistemological agency. Contemporary eco-fiction, distancing itself from the humanistic legacy of existentialism—albeit with an angry and crisis-stricken nature—also engages in redefining the human-nature relationship. This study reveals that ecological discourse has deep roots in the Islamic philosophical-literary tradition and stands in fundamental opposition to Sartrean anthropocentrism.